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OCTOBER 2013 OCTOBER 2013 || VOL. 18 VOL. 18 || NO. NO. 55
U.S. Navy’s Composite Submarine Camels
Emerging Technology: Preforms Get Serious
Pi Joint Spar Technology for Wind Blades
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Table of Contents
FEATURES
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October 2013 | Vol. 18 | No. 5
The 360Rush water slide at Spring Valley Beach amusement park in Blountsville, Ala., was designed by SplashTacular (La Quinta, Calif.). Cape Coral, Fla.-based composite tooling supplier JRL Ventures demonstrated that tooling costs can be greatly reduced by producing parts of multiple sizes from a resizable mold and a single, reusable vacuum bag (see p. 36).Source | SplashTacular
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COMPOSITESWATCH
Marine | 9
Wind Energy | 10
Construction | 12
News | 15
COLUMNS
Editor | 3CT goes to SPE ACCE
Composites: Perspectives & Provocations | 5
By the Numbers | 7
DEPARTMENTS
Work In Progress | 16
Applications | 41
Calendar | 42
New Products | 43
Marketplace | 44
Showcase | 45
Ad Index | 45
COVER PHOTO
Structural Preform Technologies Emerge from the ShadowsNot yet in full production, with one exception, all are aimed at accelerating composite part manufacture at fast automotive rates. By Sara Black
Wind Blades | Progress & ChallengesDespite doube-digit wind energy industry growth, turbine blade manufacturers and materials suppliers acknowledge a pressing need to reduce costs and innovate. By Michael LeGault
Inside Manufacturing Maximum Thrills | Minimum ToolsWater slide manufacturer’s disastrous fi re loss opens door to a closed molding process that reduces the number — and cost — of production molds, promising future gain.By Michael LeGault
Engineering Insights Composite Submarine Camels Win with Long-term DurabilityThe U.S. Navy wisely opts for more expensive submarine moorings that maximize lifecycle cost-effi ciency.By Jeff Sloan
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Editor
Composites Technology (ISSN 1083-4117) is published bimonthly (February, April, June, August, October & December) by Gardner Business Media, Inc. Corporate and production offi ces: 6915 Valley Ave., Cincinnati, OH 45244. Editorial offi ces: PO Box 992, Morrison, CO 80465. Periodicals postage paid at Cincinnati, OH and additional mailing offi ces. Copyright © 2013 by Gardner Business Media, Inc. All rights reserved.
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Postmaster: Send address changes to Composites Technology, 6915 Valley Ave., Cincinnati, OH 45244-3029. If undeliverable, send Form 3579.
Subscription rates: Nonqualifi ed $45 (USD) per year in the United States, $49 (USD) per year in Canada, $100 (USD) per year airmail for all other countries. Single issue prepaid, $10 (USD) per copy in North America, $25 (USD) in all other countries. Send payment directly to Composites Technology at Cincinnati offi ces, (800) 950-8020; fax: (513) 527-8801.
MEMBERSHIPS:
EDITORIAL OFFICES
Publisher Richard G. Kline, Jr. / [email protected] Jeff Sloan / [email protected] Managing Editor Mike Musselman / [email protected] Editor Sara Black / [email protected] Editor Lilli Sherman / [email protected] Editor Ginger Gardiner / [email protected] Graphic Designer Susan Kraus / [email protected] Manager Kimberly A. Hoodin / [email protected]
Midwestern U.S. & International Sales OfficeAssociate Publisher Ryan Delahanty / [email protected] U.S. Sales OfficeDistrict Manager Barbara Businger / [email protected], Southwest & Western U.S. Sales OfficeDistrict Manager Rick Brandt / [email protected] Sales Offi ceEuropean Manager Eddie Kania / [email protected]
Contributing Writers Dale Brosius / [email protected] Donna Dawson / [email protected] Michael LeGault / [email protected] Peggy Malnati / [email protected] Karen Wood / [email protected]
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Richard G. Kline, CBC | PresidentMelissa Kline Skavlem | COO
Richard G. Kline, Jr. | Group PublisherTom Beard | Senior V.P., Content
Steve Kline, Jr. | Director of Market IntelligenceErnest C. Brubaker | Treasurer
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Jeff Norgord | Creative DirectorRhonda Weaver | Creative Department Manager
Dave Necessary | Senior Marketing ManagerAllison Kline Miller | Director of Events
ALSO PUBLISHER OF• High-Performance Composites • Modern Machine Shop • IMTS Directory • NPE Offi cial Show Directory• Moldmaking Technology • Production Machining• Products Finishing • Products Finishing Directory• Plastics Technology / PT Handbook • Automotive Design & Production
We know what we need to do to be ready.
Jeff Sloan
CT goes to SPE ACCE
Th is year, the Society of Plastics Engineer’s Automotive Composite Conference & Exhibition (ACCE) was relocated from the outgrown Michigan State University Management Education Center (Troy, Mich.) to the Suburban Collection Show-case in nearby Novi. A good thing. ACCE exhibitors doubled, and last year’s record 630 attendees paled compared to the 897 registered this year — one indication that auto OEMs could be ready for pervasive use of composites. CT staff ers went looking for answers to the question I asked in my August editorial: Are we ready? Th e best answer may be, We know what we need to do to be ready.
Managing editor Mike Musselman says many at ACCE considered that very question. ACCE co-chair Ed Bernardin (Siemens PLM Soft ware) said the auto industry’s characteristic high rate of change is a key hurdle. He and Roger Assaker (e-Xstream engineering) contended that virtual testing of composites is a huge need in the auto world. Such tools are well developed for chopped-fi ber compounds, but there is a pressing need for soft ware that can simulate failure of continuous-fi ber composites. Reliable tools are emerging and will, says Assaker, take a two-year, multimillion dollar testing program and compress it into a long work day!
High-pressure RTM (HP-RTM), the subject of multiple research reports at last year’s ACCE, is now commercial: Shuler SMG GmbH’s vacuum-assisted HP-RTM system mints the BMW i3 passenger cell and the BMW M3 roof. Quickstep Technologies proposes to do similar duty at low pressures (and with less expensive equipment), with the aid of fl uid heating and its new Resin Spray Technology (RST). And Volkswagen AG’s Hendrik Mainka said his work with Oak Ridge National Lab shows that lignin precursor and the process of oxidation and pyrolization that converts it to carbon fi ber spells cost savings of 40 percent. Unfortunately, unresolved issues, among them the seasonal variation in lignin (as a plant product), mean commercialization could be a decade away.
CT senior technical editor Sara Black points out that ACCE’s “Aluminum & Composite — Compete or Collaborate?” panelists included aluminum industry representatives. All the panelists agreed that composites can 1) displace steel and aluminum in appropriate applications, and 2) make invaluable contributions to lightweighting. But the discussion revealed that auto OEMs will remain resistant until they hear a valid value proposition. If a composites solution for automotive can make a part lighter, for less money, no problem, say the OEMs. Such solutions, so far, are scarce — a notable exception is the semi-convertible sunroof frame for the Citroen DS3 Cabrio, molded from a modifi ed glass-reinforced styrene maleic anhydride (SMA) resin. Th e part off ers signifi cant material cost savings, part inte-gration (seven parts combined into one) and a 40 percent weight reduction. Th at aside, Kaiser Aluminum’s Doug Richman made the point that without a solid busi-ness case, it’s impossible to make the technology case. Panelist Jai Venkatesan of Dow Chemical Co., pointed out in his keynote address that adoption of compos-ites is a “high-risk, high-reward” and disruptive step, and it’ll take time. Yet, he believes that we can use lessons learned from veterans of aerospace composites and automotive aluminum, apply soft ware tools more widely, and — in collaboration — eventually ensure that composites become an entrenched material choice.
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5
Composites: Perspectives & Provocations
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n 1859, Th omas Austin imported 24 wild rabbits from England and released them into the Victoria, Australia, countryside to
provide animals for sport hunting. Th e rabbits, doing what rabbits notably do, multiplied voraciously, destroying vegetation and crops as they spread north and west across the continent. With no natural predators in Australia, the rabbit population rose to an estimated 10 billion by the late 1920s. Th e world’s longest rabbit fence, stretching 1,138 miles/1,831 km from north to south in Western Australia, was erected with only limited success. Although Austin’s intentions might have been good, the outcome was anything but.
Such stories exemplify the prover-bial law of unintended consequences, in which what is believed to be a simple solution to a problem runs into a complex system of in-teractions that leads to a negative outcome. A more recent example is regulation that drives the production of ethanol as a fuel additive to reduce oil imports, but then drives up the demand for corn, re-sulting in higher food prices.
Some argue that government regulations always have detrimen-tal consequences, but one only has to visit Shanghai, China, to be reminded that the 1970 Clean Air Act in the U.S. has been a positive for our major cities. Th ere was considerable gnashing of teeth and claims of economic peril in the wake of the law’s passage, but out of the law arose a lot of new pollution-control technology, both for automobiles and smokestack industries. Th e composites industry benefi tted because of the inherent corrosion resistance of polyesters and vinyl esters used in scrubbers and effl uent piping.
In the composites industry, we have seen several decades of reg-ulations targeting styrene, out of concern about air pollution and suspected carcinogenic toxicity. Styrene is an extremely important and cost-eff ective reactive diluent for polyester and vinyl ester res-ins, enabling the low viscosities needed to promote fl ow, sprayabil-ity and wetout of fi berglass and other reinforcements. Legislation, starting with California’s Proposition 65 and the later U.S. Environ-mental Protection Agency’s (EPA) Maximum Achievable Control
The positive consequences of regulating styrene
Bio | Dale BrosiusDale Brosius is the head of his own consulting company and the president of Dayton, Ohio-based Quickstep Composites, the U.S. subsidiary of Australia-based Quickstep Technolo-gies (Bankstown Airport, New South Wales), which develops out-of-autoclave curing processes for advanced composites. His career includes a number of positions at Dow Chemi-cal, Fiberite and Cytec, and for three years he served as the general chair of SPE’s annual Automotive Composites Con-
ference and Exhibition (ACCE). Brosius has a BS in chemical engineering from Texas A&M University and an MBA. Since 2000, he has been a contributing writer for Composites Technology and sister magazine High-Performance Composites.
The performance of composites produced with polyesters and
vinyl esters has greatly improved, making composites
ever more competitive.
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Technology (MACT) standards, was met initially by strong opposi-tion from the composites industry supply chain, citing large reduc-tions in industry employment and loss of competitiveness against foreign rivals that aren’t restricted by such legislation.
Having observed the long-term eff ects of these regulations, I am fi rmly of the opinion that their consequences have been mostly positive, well beyond worker safety and reduction of VOCs. How? Th e quality and performance of composites produced with poly-esters and vinyl esters have greatly improved, making composites ever more competitive against traditional materials, such as wood, concrete and metals. I’m not sure these advances would have been achieved if the industry hadn’t been pushed out of its comfort zone.
Take, for example, the large-scale migration from open mold-ing to closed molding, in particular, the growth of vacuum resin infusion (in all its various forms and acronyms). Rather than thick, resin-rich parts made by chopper guns and manual rolling, today’s boats, bridge decks, wind turbine blades and pollution-control sys-tems incorporate structural multidirectional fabrics and use less
resin, yielding thinner, lighter and stron-ger structures. A whole industry has de-veloped to support large-part infusion, resulting in greater competitiveness and new jobs. Where open molding is still preferred, sprayup is done by robots following a preprogrammed path. Th e result is less part-to-part variation and
less resin use. Styrene contents of 45 percent used to be standard. Reformulation and new chemistries have reduced this to 25 to 30 percent in many cases. Filament winding, pultrusion and compres-sion molding also have benefi tted from these new resins. Workers are better protected, fewer VOCs are emitted, and the industry is more competitive.
We have all of the above thanks to an industry full of talented scientists and engineers, and the future of styrene-diluted compos-ite resins looks positive. But there is still one major battle to fi ght: the listing of styrene as a suspect carcinogen in the 12th Report on Carcinogens (ROC), issued by the National Toxicology Program (NTP). Fortunately, through the excellent eff orts of the American Composites Manufacturers Assn. (ACMA, Arlington, Va.) and oth-er industry groups, the National Research Council (Washington, D.C.) has agreed to conduct a peer review of the NTP’s listing. Here is a situation where we should not err on the side of caution. Instead, we should trust the real science that shows styrene is safe, and I am optimistic that the right outcome will prevail.
And that rabbit problem in Australia? Th rough the introduction of virus-carrying insects starting in the 1950s, today’s population is estimated at 200 million, a 98 percent reduction since 1930. It’s one more example of good science and innovative technology meeting the challenge. | CT |
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By the Numbers
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n July, the Composites Business Index (CBI) of 47.7 indicated that composites business activity in the composites industry
had contracted for the second consecutive month, having moved steadily lower since it had peaked in March. Employment was the only index to make a positive contribution in July, expanding for the fi ft h straight month. All other subindices performed worse in July than in June. New orders contracted for the third month and at a slightly faster rate. Production moved from growth to contrac-tion for the fi rst time this year. Backlogs continued to contract, and did so more signifi cantly and at their fastest rate for the year
to date. Exports remained mired in contraction. Supplier deliveries lengthen in July, having done so at a fairly constant rate all year.
Material prices increased in July. Th e rate of increase reached its fastest pace since March. Prices received by composites fabrica-tors decreased for the third time in four months. Th e combination of increasing material prices and decreasing prices received had a signifi cant negative impact on profi tability. But future business ex-pectations improved noticeably in July. Th ey reached their second highest level since May 2012.
Th e business activity this year through July was much higher at large than at small facilities. Th ose with more than 250 employees had grown at a consistently strong rate since December 2012. Facili-ties with 50 to 249 employees had grown in all but a couple of months in that same time period. However, fabricators with fewer than 50
Composites Business Index 48.2: Contraction begins to slow
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Bio | Steve KlineSteve Kline is the director of market intelligence for Gard-ner Business Media Inc. (Cincinnati, Ohio), the parent com-pany and publisher of Composites Technology magazine. He started as a writing editor for another of the company’s magazines before moving into his current role. Kline holds a BS in civil engineering from Vanderbilt University and an MBA from the University of Cincinnati.
employees had, through July, contracted four straight months. Th e smallest facilities (fewer than 19 employees) contracted in July at the fastest rate since the CBI began in December 2011.
In July, the strongest region for the year was the West North Cen-tral, which had grown for fi ve straight months. Th e Mountain region experienced the fastest growth rate in July, and it was its fi rst month of growth since February this year. All other regions contracted in July.
Future capital spending plans were at their second lowest level in July since June 2012. Planned spending was more than 25 percent above the historical average. Compared to July 2012, spending plans in July 2013 were up by 16.1 percent.
In August, a CBI of 48.2 showed that composites industry busi-ness activity had contracted for the third consecutive month, but the rate of contraction had slowed, indicating a possible break with its downward trend. Two subindices made positive contributions: Employment grew for the sixth straight month, and suppler deliver-ies continued their long-term lengthening trend. Production and exports continued to contract in August but did so at slower rates. Exports, in particular, had contracted at a steadily slower rate since
December 2012. New orders con-tracted for the fourth consecutive month. Th e only subindex to nega-tively impact the CBI was backlogs. In August, it contracted for the 15th month and had done so noticeably faster each month since February.
Material prices increased in August at their slowest rate since November 2012. Prices received increased slightly aft er decreasing three of the previous four months. Future business expectations fell somewhat aft er having stayed fairly level for six months.
One month does not a trend make, but activity based on plant
size could be shift ing. Fabricators with more than 250 employees contracted for the fi rst time since November 2012. Th ose with fewer than 19 employees continued to contract, but at a much slower rate. Th e small facility index, however, moved up to 43.9 from 38.9 in July. Th ose with 50-249 employees continued strong.
Four regions expanded in August. Th e fastest rate was the West South Central, which had grown fi ve of the previous seven months and, thus, was 2013’s best performer to date. Meanwhile, New Eng-land, the South Atlantic and the Middle Atlantic all moved from contraction to expansion. But the West North Central, which had strong growth the previous fi ve months, fell off sharply.
Future capital spending plans were just above the historical av-erage in August. However, the month-over-month rate of change contracted for the third time in fi ve months. | CT |
THE COMPOSITES BUSINESS INDEX
Subindices August July Change Direction Rate Trend
New Orders 47.4 47.4 0.0 Contracting Flat 4
Production 49.0 48.0 1.0 Contracting Slower 2
Backlog 39.7 41.0 -1.3 Contracting Faster 15
Employment 51.9 51.1 0.8 Growing Faster 6
Exports 48.3 46.7 1.6 Contracting Slower 16
Supplier Deliveries 52.6 51.7 0.9 Lengthening More 21
Material Prices 58.4 64.5 -6.1 Increasing Less 21
Prices Received 50.3 48.3 2.0 Increasing From Decreasing 1
Future Business Expectations 65.4 67.8 -2.4 Improving Less 21
Composites
Business Index48.2 47.7 0.5 Contracting Slower 3
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COMPOSITES WATCH
Composites WATCH
Whether it’s the marine market, the wind energy industry, urban
infrastructure or the composites supply chain, the key word is change.
MARINE market’s glass half full, half empty
SAMPE/ACMA joint trade show christened CAMX
MAR
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No end-market served by the composites industry was harder hit by the recession than marine.
Since 2008, demand for boats of all types has dropped dramatically. U.S.-based BoatingIndustry.com hosted a webinar in August in which three speakers agreed that the marine segment could take a while to return to the peaks seen in 2005-2006. Jim Petru, director of industry statistics and research at the National Marine Manu-facturers Assn. (NMMA, Chicago, Ill.); Peter House-worth, director of client services at Info-Link (Miami, Fla.); and Jon Burnham, editorial director at Dominion Marine Media (Norfolk, Va.) noted a number of posi-tives: Boating participation has been up 32 percent in the past fi ve years, 81 percent of boat owners have annual incomes of less than $100,000, powerboat sales were up 10 percent and sailboat sales were up 29 percent in 2012. Further, the total U.S. recreational marine craft sales were $35.6 billion in 2012, up from $32.4 billion in 2011, but still shy of the 2006peak of $39.5 billion.
Th at said, they spied troubling trends as well: Each year, the average age of boat owners increases by six months. Trad-tional powerboat sales are in decline, with 157,000 units sold in 2012, compared to more than 500,000 units sold in 1988. Th e average powerboat age today is 21 years, compared to 15years in 1997, and 74 percent of sailboats are more than 20 years
old. Th e total number of marine vessels registered in the U.S. hasn’t changed in 15 years, despite a 25 percent population increase, and 7 out of 10 fi rst-time boat buyers sell their boat and leave the sport. Lastly, aging baby boomers, a long-time major consumer of boats, are less active in the sport.
Analysts suggest that the aging fl eet might signal that consumers are on the verge of upgrading to new boats, propelling the market into high-growth. Petru noted during the webinar that overall boat sales correlate to consumer confi dence. Because that confi dence is coming back slowly and the market is awash with quality used boats for sale, the marine industry’s growth will likely continue to be slow.
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those in the marine, wind energy, automotive, infrastructure and industrial markets. Going forward, CAMX is expected to be North America’s composites industry go-to event for every served mar-ket segment. Th e newly partnered organizations say the trusted and valued aspects of both organizations’ annual events will continue at CAMX in an expert-rich combined technical conference program, and a far more expansive show fl oor. Th e fi rst CAMX conference program will take place Oct. 13-16, 2014, and the CAMX exhibit hall will be open Oct. 14-16, at the Orange County Convention Center in Orlando, Fla. CAMX 2014 is expected to attract more than 8,500 attendees and more than 500 exhibitors. For more infor-mation, visit the CAMX Web site at www.thecamx.org.
Th e Society for the Advancement of Material and Process Engineer-ing (SAMPE, Covina, Calif.) and the American Composites Manu-facturers Assn. (ACMA, Arlington, Va.) announced on July 31 that their new jointly owned and operated trade show and conference will be called CAMX — the Composites and Advanced Materials Expo. SAMPE and ACMA, which traditionally have operated their own trade shows, announced late in 2012 that they would consoli-date the former SAMPE show and ACMA’s COMPOSITES show into a single fall event, beginning in 2014.
SAMPE brings with it composites professionals who primarily serve the aerospace market and other advanced materials applica-tions. ACMA has served a broad range of applications, including
COMPOSITES WATCH
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TPI Composites (Scottsdale, Ariz.) announced on Aug. 13 that it had signed a multiyear supply agreement with Nordex SE (Hamburg, Germany) under which it will provide blades for Nordex’s N117 wind turbine from TPI’s factory in Izmir, Turkey. Nordex will use the blades for projects in Turkey and export them to other locations in the greater European region, northern Africa and the Middle East.
TPI and ALKE ÎNŞAAT, an engineering, manufacturing and construction company headquartered in Istanbul, Turkey, formed a joint venture company in Izmir to manufacture large blades in
WIND BLADE joint venture to supply Europe and North Africa
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COMPOSITES WATCH
2012. Th e joint venture, TPI Kompozit Kanat Sanayi ve Ticaret A.S., has a 355,000-ft 2 (32,500m2) building with convenient access to both land and water transportation, which enables cost-eff ective export of blades to southern and eastern Europe and northern Afri-ca. TPI Composites controls and operates the Turkish joint venture.
“We are thrilled to add Nordex as a key customer of our Tur-key operation under TPI’s partnership model,” says Steve Lockard, president and CEO of TPI Composites. “Nordex is a leader in the Turkey and European wind markets. Th eir N117 turbine is one of the most advanced and effi cient in its class with average capacity factors in excess of 35 percent.” Dr. Juergen Zeschky, CEO of Nor-dex, adds, “We are very pleased to be partnering with TPI in Turkey to provide world-class wind blades to the region. TPI’s track record as a technology and quality leader makes them an excellent partner to match the performance and reliability of Nordex wind turbines.”
Related to wind energy market growth in Eurasia, Reuters reported on Aug. 26 that wind turbine and blade producer Sie-mens (Munich, Germany) expects the global wind power market to more than quadruple by 2030, lift ed by strong growth in Asia. Markus Tacke, chief executive of Siemens’ wind power division, said at a renewable energy conference in Berlin that “the market will shift away from Europe signifi cantly,” according to the story by Christoph Steitz. Tacke added that globally installed wind pow-er capacity would increase to 1,107 GW in 2030 from 273 GW in 2012, with the Asia-Pacifi c region accounting for more than 47 percent of the total, up from 34 percent now.
COMPOSITES WATCH
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A 3-D carbon fi ber reinforcement recently developed by SGL Group - Th e Carbon Co. (Wiesbaden, Germany) and V. FRAAS Solutions in Textile GmbH (Helmbrechts, Germany) has recently proven its worth. SGL reported on Aug. 16 that it is possible to produce concrete façade panels only 26 mm/1.02 inches thick using a “carbon grid” as internal reinforcement. Th e grid consists
of two plies of carbon fi ber scrim spaced 12 mm/0.47 inch apart that are connected by compression-resistant pile threads. A steel-reinforced facade panel of similar size reportedly has a minimum thickness of 100 mm/3.94 inches — the extra thickness is neces-sary to prevent corrosion of the steel due to water ingress by way of cracks in the concrete.
Th e thin facade panels were installed on a new factory for Al-phabeton AG in Bü ron, Switzerland, an innovative specialist in concrete products manufactured from high-performance and ultrahigh-performance concrete (UHPC). A ventilated façade “curtain wall” was installed on the building, with a total area of 450m2/4,844 ft ². Th e wall comprises 350 panels, each measur-ing 865 by 1,620 mm (34 by 63.8 inches), with a thickness of 26 mm/1.02 inches. Th e building, appropriately, houses a precast concrete element production line.
“We were looking for a solution that would enable us to pro-duce thin concrete façade panels in large dimensions,” says Alpha-beton’s Hans-Peter Felder, who is responsible for R&D. “Th e new 3-D carbon fi ber grids impressed us with their light weight and corrosion resistance and were easy and convenient to process.”
Peter Weber, VP of sales and marketing for SGL’s Carbon Fi-bers & Composite Materials business unit, adds, “In this applica-tion, we particularly exploit the corrosion resistance of our car-bon fi bers. Th anks to this advantageous property, we can dispense with the thick concrete covering obligatory with steel-reinforced concrete to prevent rust and produce thin concrete elements.”
V. FRAAS has developed a production plant in which the new 3-D textile reinforcement is manufactured with SGL’s SIGRAFIL C carbon fi bers, in large dimensions. Th e structural grids are also being used in the repair and renovation sector and in bridges and buildings, says V. FRAAS.
CON
STR
UCTI
ON New composite reinforcing
grid enables thinner concrete façade panels
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FMS-100™ a streak-free, solvent-based mold release sealer that offers ease of application, high gloss finish and fast cure. Eliminates porosity/micro porosity, and even seals “green” molds and repaired areas.
AQUALINE® ™ a water-based emulsion that sets the standard for water-based release agents. Nonflammable. Multiple releases per application.
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COMPOSITES WATCH
Stephen Browning, PE, joined Strongwell Corp. (Bristol, Va.) as a struc-tural engineer. He has a BS in civil engineering technology from Bluefi eld State College, a BS in civil and environmental engineering from Tennes-see Tech University and an MS in civil engineering from Virginia Tech. From 2004 to 2013 he operated his own construction design/consulting business … The Composites Group (Highlands Heights, Ohio) realigned its senior management. Hector Diaz-Stringel was promoted to VP of manufacturing operations. He worked in the chemicals industry before joining the company as corporate director of manufacturing operations in 2012. Diaz-Stringel holds a BS in chemical engineering and manage-ment from the Monterrey Institute of Technology and Higher Education (Monterrey, Mexico) and an MBA from Kent State University. Dwight Morgan became VP of sales and marketing. He began his career with M.A. Hanna Co. (Cleveland, Ohio), now Avon Lake, Ohio-based PolyOne Corp., then formed color and additive formulator Accel Color Corp. (Na-perville, Ill.), now part of Techmer PM LLC (Clinton, Tenn.). Morgan holds a BA from Kent State University’s School of Journalism and a JD from the University of Akron School of Law. Company veteran Marc Imbrogno was promoted to corporate director, market/product development. He began his career as an R&D chemist at Cleveland, Ohio-based Glastic Corp. and then joined BASF (Florham Park, N.J.). He holds a BS in chem-istry from the University of Akron … Robert Scarpitto has joined the Interplastic Corp. (St. Paul, Minn.) sales team as a sales representative responsible for California, Nevada and Baja California, Mexico. He brings to the position more than 20 years in a variety of sales positions.
PEOPLE BRIEFS
www.dieffenbacher.com
With our new, innovative D-SMC and HP-RTM processes, we are continuously advancing global progress in series pro-duction of lightweight components with glass or carbon fibre-reinforced plastics.
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EUROPE
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Messe Stuttgart,
Germany
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COMPOSITES WATCH
Chem-Trend (Howell, Mich.), reported on July 15 that it has acquired Zyvax Inc. (Ellijay, Ga.). Zyvax will become a brand within the Chem-Trend product mix.
Zyvax was founded in 1985 by Nancy Layman, who was an early leader in, and dedicated most of her career to, developing specialty release systems for the composites industry. Zyvax was fi rst to market with a line of solvent-free, water-based release systems engineered to meet the require-ments of advanced composite processes. Layman is working with Chem-Trend and Zyvax customers for a successful integra-tion of the Zyvax product line into the Chem-Trend portfolio.
Dieff enbacher (Eppingen, Germany) reported Sept. 13 that it had purchased machinery, expertise and intellectual prop-erty rights to the Relay automated tape-laying technology, developed by recently shuttered Fiberforge (Glenwood Springs, Colo.) to lay up fl at thermoplastic compos-ite “tailored blanks” for subsequent ther-moforming as 3-D components.
Dieff enbacher intends to pursue appli-cations using fi ber tape structures alone, but also plans to integrate the tape layup technology into its LFT-D system to create Tailored LFT-D technology. Th e resulting components, with local UD-fi ber tape re-inforcement for specifi c applications, will subsequently be integrated into large-scale production lines to achieve high levels of structural rigidity at a low cost.
On Aug. 27, Axson Technologies (Cer-gy, France, and Eaton Rapids, Mich.) an-nounced that it has acquired CASS Poly-mers of Michigan Inc. (Madison Heights, Mich.). It will be integrated into Axson US Inc. (Eaton Rapids, Mich.), and Axson Technologies will manage the acquired business and brands, which include Tool Chemical Composites (TCC), ADTECH Plastic Systems, ADTECH Marine Systems and Spartite.
According to Axson, the acquisition fortifi es its focus on providing high-per-formance polymer formulations to the tooling, prototyping, structural adhesive and composites markets globally and,
more specifi cally, in North America. Axson will continue to off er the TCC, ADTECH Plastic Systems, ADTECH Marine and Spar-tite lines, which include well-known trademarked products, such as Model Plank, Pattern Plank, Die Plank, Fixture Plank, ProBuild and other ADTECH Marine products.
Composites NEWS
Chem-Trend acquires Zyvax, Dieffenbacher buys Fiberforge, Axson US integrates CASS Polymers
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Wind blades are commonly made by infusing top and bottom blade shells separately, then adhesively bonding them together around a prefabricated shear web.
Th e current state of the art leaves much to be desired. Th e typical construction is essentially an I-beam, in which a C-shaped shear web provides an area for adhesive bonding to spar caps that are co-infused with the blade shell. Typically, the C-beam must be braced with additional L-beams during assembly (see left image, top of p. 25). Aft er epoxy paste adhesive is applied to the bottom blade half and the shear web, their surfaces are mated, and suffi cient time must be allowed for cure. Th en, adhesive is applied to the top blade half, the upper surface of the shear web and the leading and trailing edges. Again, the adhesive surfaces are mated, and time is required for cure. Th is multistep process requires signifi cant labor and time. Additionally, when the top half of the blade is lowered onto the bottom half, the joints are mated blindly, that is, without visual or other access to the bonding areas. Industry presentations and patents list other shortcomings and clearly state that blade designs would benefi t from an improved bond confi guration between the shear web and spar cap.
Textile manufacturer 3TEX (Cary, N.C.) began work on such a confi guration several years ago as part of a Small Business Innova-tion Research (SBIR) project awarded by the U.S. Department of Energy (DoE, Washington, D.C.), using the Pi joint concept that was demonstrated in the Air Force Research Lab’s (AFRL, Dayton, Ohio) Composites Aff ordability Initiative (see “Learn More,” p. 29).
WHY PI?
3TEX cites two reasons for its use. First, the Pi joint (so named because its primary component takes the shape of the Greek letter π) have been shown in the aerospace industry to provide superior strength in pull-test loads, compared to conventional laminated joints. AFRL’s Dr. John Russell says the joint “provides symmet-rical loads to the adhesive area and acts as a double lap-shear joint, increasing the surface area for bonding.” Also, the primary load in the adhesive bonds is located farther away from the area of maximum strain. Th ese factors combine, says Russell, to make the Pi joint a more eff ective design. Pi joints also have demonstrated high tolerance of several manufacturing defects associated with
Wind blade structural elements are typically a shaped shear web
bonded to spar caps co-infused into top and bottom blade shell
halves. The thick and uneven adhesive layers limit the strength of
the joint and create reliability and repair issues.
Supporting spar
Adhesive layer
Composite shell
Composite shell
Spar
Easily co-infused structural joint increases ultimate strength and fatigue life,
offering solutions for designers as blades get longer and move offshore.
Wind blades
Pi preforms increase shear web failure load
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blind mating, including excessively thick bondlines, voids, nonver-tical alignment of the Pi legs or joint structure within the Pi, and even peel plies that are not removed before bonding.
Second, a Pi joint, despite its complexity, can be preformed in an automated process. 3TEX R&D director Dr. Keith Sharp says his company’s 3D Weaving process “lends itself to easy manufacture of Pi joint preforms. We simply design a textile with z-direction yarns penetrating completely through the thickness for the center portion and then only halfway through the thickness for the outer edges, allowing these lengths to be folded up to form the two legs of the Pi.” Th e dry preform is reportedly easy to co-infuse with the blade shell so the legs of the Pi align vertically to receive and locate the shear web. Th is permits the blade manufacturer to use a simple fl at plate for the web — C-shapes and L-braces are no longer necessary. Th erefore, blind mating of the joint surfaces is vastly simplifi ed.
PI PROGRESS
In a presentation at the 2012 SAMPE conference in Baltimore, Md., 3TEX reported that preliminary performance testing was done by fabricating composite I-beams made with the 3TEX 3-D woven Pi preform joint and a conventional joint (C-beam plus L-shaped braces, see top images, this page). Th e I-beams were 2.7m/8.9-ft long by 0.3m/1-ft tall, with 0.2m/0.7-ft wide fl anges, matching the dimensions of the spar cap width and thickness and the shear web height of a 13m/42.7-ft long commercial wind blade at the 10m/33-ft station. Th e fl anges were 8.1-mm/0.3-inch thick E-glass/epoxy laminate. A test apparatus was developed that clamped a stan-dard I-beam at one end and applied an upward load at the other end to simulate the dominant type of loading on a wind blade.
For the Pi joint I-beams, Pi preforms were woven as a single E-glass fabric and split to form two 4.2-mm/0.2-inch thick legs, each measuring 42.5 mm/1.7 inches in length and separated by an 8.1-mm/0.3-inch thick central section that was 25-mm/1-inch wide. Th e 110-mm/4.3-inch wide preform had 54 percent total fi ber vol-ume fraction with equal amounts of fi ber in both in-plane directions and 1.5 percent in the z-direction. A 20-mm/0.8-inch wide fl at plate shear web was made, using 3.8-mm/0.2-inch thick faceskins of tri-axial E-glass fabric from SAERTEX USA LLC (Huntersville, N.C.) on each side of a 12.4-mm/0.5-inch thick balsa wood core, supplied
by distributor LBI Inc. (Groton, Conn.). Th e Pi joints and web were infused with Rhino 1401-21/4101-21 epoxy resin supplied by Rhino Linings (San Diego, Calif.). When the Pi joints and web were bond-ed, the Pi joint slot was 2.5 mm/1 inch wider than the web to allow suffi cient space for the Rhino 405 Structural Epoxy Gel adhesive.
Th e conventional I-beam used in the test replicated the construc-tion of a 13m/43-ft long commercial wind blade from Heartland En-ergy Solutions (Mount Ayr, Iowa). Th e C-shape shear web was made with two faceskins of triaxial E-glass fabric (0˚/±45˚ with 0˚ orient-ed along the beam length), each measuring 3.8-mm/0.15-inch thick, on each side of a 12.4-mm/0.5-inch thick balsa wood core. Th e ma-terial suppliers and infusion process were the same as those previ-ously described. Th e top and bottom fl anges of the C-beam were formed by extending the two faceskins at 90o to the cored section. Th e C-beam measured 7.6-mm/0.3-inch thick, and its height was 50 mm/1.97 inches. Two 7.2-mm/0.28-inch thick L-beams were
3TEX tested I-beams
made with a conventional
joint design (C-beam plus
L-shaped braces, at left)
vs. its new joint design
using a 3-D woven Pi
preform (right).
Both types of 2.7m/8.9-ft beams were clamped and cantilever-loaded to
simulate wind blade service, during tests conducted at the Constructed
Facilities Laboratory at North Carolina State University.
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7.6 mm thick
L-shape(7.2 mm thick)
Adhesive Layer(3.0 mm thick)
Flange(8.1 mm thick)
C-leg
C-leg
Balsa core(12.4 mm thick)
Shear web skin (3.8 mm thick)
Adhesive layer(3.0 mm thick)
Pi base
Balsa core(12.4 mm thick)
Adhesive Layer(2.5 mm thick)
(4.2 mm thick)
(8.1 mm thick)Co-infused Pi joint and blade skin
Pi preform
Pi leg
Shear web skin(3.8 mm thick)
Flange
50 mm
200 mm 200 mm
42.5 mm
300 mm
25 mm
110 mm
CONFERENCE CO-CHAIRS: ANDREW HEAD, President, A & P Technology Inc. DOUG WARD, Consulting Engineer, Composites. GE Aviation
SPONSORED BY:
IN ASSOCIATION WITH:
Sponsorships and exhibit space are available! Contact Kim Hoodin, Marketing Manager, [email protected]
Join us in Knoxville, Tennessee for Carbon Fiber 2013! Don’t miss this opportunity to learn from the industry’s leading innovators and network with decision makers and key executives from all aspects of the carbon fiber supply chain!
Plan to join us for a tour of Oak Ridge National Laboratory’s carbon fiber manufacturing facility (optional).
REGISTER TODAY!YY!! DECEMBER 9-12, 2013
TO LEARN MORE OR REGISTER VISIT:
http://short.compositesworld.com/CF2013
LEARN!CompositesWorld’s Carbon Fiber 2013 is the Carbon Fiber conference organized by composites industry professionals! Since 1998 the Carbon Fiber conference has successfully been bringing together the industry’s leading executives and technologists to explore the expanding role of carbon fiber
in the composites industry.
NETWORK!Nowhere else will you have access to this timely and pertinent information and to the industry’s top minds and innovators. As you enjoy the catered networking functions at Carbon Fiber 2013 you will make invaluable contacts with the key executives in the industry.
Pre-Conference Seminar*Monday, December 9, 2013
Emerging Opportunities and Challenges for Carbon Fiber in Passenger Automobiles – Is the CFRP Industry Ready for Mass Production?Presented by:Chris Red, Principal, Composites Forecasts and Consulting, LLC
The seminar provides a “grounds-up” analysis of the market and opportunities for CFRP within the 75 million vehicles per year passenger vehicle market over the next ten years (2013 – 2022), with a special focus on:
• Drivers and Limitations Influencing CFRP Usage• Regional and OEM activity analysis• CFRP applications (body, chassis, drivetrain, brakes, interiors, etc.) analysis• Tier supplier activity• Manufacturing process considerations• CFRP component volumes and raw material requirements to support
forecasted automobile production.
*Separate fee required
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CONFIRMED PRESENTATIONS INCLUDE:
Producing Thermoplastic Matrix Composites for Aeronautical Applications Under Industrial Scale ConditionsANGELOS MIARIS, Premium AEROTEC GmbH
Analysis and Optimization of Composite Structures – Challenges and Opportunities BRETT CHOUINARD, COO, Altair
Next Generation Carbon Fiber Composites: Beyond Medium VolumeGARY R. LOWNSDALE, Chief Technology Officer, Plasan Carbon Composites
Carbon Fiber Powering America’s Big RigsNEEL SIROSH, Chief Technology Officer, Quantum Technologies Inc.
A Hybrid Composite/Metal Gear Concept for Rotorcraft Drive Systems GARY D. ROBERTS, Research Materials Engineer, NASA Glenn Research Center
Alternative Precursors for Sustainable and Cost-effective Automotive Carbon FibersHENDRIK MAINKA, Volkswagen Group of America, Inc.
Application and Processing of Complex Fabrics for Lightweight StructuresCHRIS MCHUGH, Technical Manager, Sigmatex (UK) Ltd
Lighter, Stronger, Greener: How Carbon Fiber is Modernizing Precast Concrete!JOHN M.CARSON, Executive Director, AltusGroup, Inc
Carbon Fiber Usage in the Wind Energy IndustryAARON BARR, Technology Advisor, MAKE Consulting
Automotive Light Weighting Opportunities & ChallengesPROBIR GUHA, Vice President, R&D - and -MIKE SIWAJEK, Director, Research, Continental Structural Plastics
AND MANY MORE!For an up-to-date agenda and abstracts, please visit:
http://short.compositesworld.com/CF2013
Crowne Plaza KnoxvilleKnoxville, Tennessee, USA
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adhesively bonded to bolster the C-beam. Spacers held the bondline thickness to 3 mm, ±0.3 mm (0.1 inch, ±0.01 inch).
Sharp says three conventional joint beams and fi ve Pi joint beams were tested at the Constructed Facilities Laboratory at North Caro-lina State University (Raleigh, N.C.). Th e Pi joint beams failed at an average 12 percent higher load and 20 percent higher defl ection than the conventional beams. Th at diff ered slightly from SAMPE paper data: “Th ose results included only three of the Pi joint tests and one of those underwent hysteresis loading. When we tested ad-ditional Pi joint cantilever beams without the hysteresis loading, the averages increased for both load and defl ection at failure.”
Notably, the failure in the Pi joint beams resulted from buckling in the shear web, not failure in the Pi joint. Th e buckling forced the vertical legs of the Pi joint outward and, in turn, caused failure in the adhesive layer. Sharp asserts that increasing the shear web’s buckling resistance would likely produce an even higher failure load. However, this is not the case for the conventional joint beams, in which failure occurred within the adhesive layer fi rst without any onset of buckling. Not least, the Pi joint beams also cost approximately 15 percent less to produce (see Table 1, below). Sharp sums up, “Manufacture using co-infused 3-D woven Pi joint preforms requires fewer steps, less fi ber, less resin and less adhesive than conventional joint manufacturing.”
Testing was extended to commercial-type construction of 13m blades. One blade with each joint type was tested under static load. Another pair was fatigue tested. Under static load the Pi-jointed blade failed at a 20 percent higher load and 25 percent greater de-fl ection than the conventional blade. Even more dramatic were the results of fatigue tests. Th e test cyclically loaded the blades to 100 percent of the test load (design load plus a factor) for 1 million cy-cles, then it increased the load by 20 percent for each 200,000 cycles until failure. Th e blade with the conventional joint failed during the 160 percent load step aft er 1.45 million cycles. Th e Pi joint blade
3TEX confi rmed I-beam test results via static and fatigue testing on 13m
/42.7-ft long commercial-type wind blades.
3-D woven textiles are stitched through the entire thickness in the center,
but only partially through at the outer edges. This allows portions of the
reinforcement stack to fold at right angles to form the Pi “legs.” The legs
form a slot that receives the shear web, with enough additional space to
allow for adhesive (light green). These preforms are easily co-infused with
the blade shell halves to receive and locate the blade shear web.
Table 1: Manufacturing steps and relative costs for I-beams
that use each joint type.
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Conventional Joint (C-beam with L-shaped braces) 3-D Woven Pi Joint
1. Infuse shear web in C-shaped mold 1. Infuse shear web
2. Cut and trim shear web 2. Cut and trim shear web
3. Infuse two L-brace composites in molds 3. Co-infuse spar caps and Pi joint preforms
4. Cut and trim L-brace composites 4. Cure shear webs and spar caps
5. Infuse spar caps 5. Apply adhesive layer to Pi joints
6. Cure spar cap, shear web, and L-braces 6. Insert shear web into top and bottom spar cap/Pi joints
7. Apply adhesive layer to bottom spar cap 7. Cure composite I beam.
8. Attach C-shaped shear web
9. Apply adhesive layer to one L-brace Relative costs of each joint type
10. Attach L-brace to spar cap and shear web C with L Pi
11. Cure epoxy putty adhesive Material Costs 0.17 0.16
12. Apply adhesive layer to top spar cap Epoxy Costs 0.22 0.19
13. Attach top spar cap to structure Labor Costs 0.61 0.50
14. Apply adhesive layer to one L-brace Total Costs 1 0.84
15. Attach L-brace to spar cap and shear web
16. Cure composite I-beam
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Read this article online | http://short.compositesworld.com/G669Zx6I.
Guest columnist David Russell described the multiple advantages of Pi joints in “The Composites Affordability Initiative, Part I” | HPC March 2007 (p. 9) | http://short.compositesworld.com/DaWuNQ7U.
One potential destination for Pi joint technology is a U.K.-based Energy Technologies Institute (ETI) blade design project contracted to Blade Dynamics (Isle of Wight, U.K.) | “Blade Dynamics receives investment for new wind blade design” | http://short.compositesworld.com/qC2iQSpC.
Senior EditorGinger Gardiner is a senior editor on the staff of Composites Technology, based in Washington, [email protected]
surpassed this, withstanding more than 700,000 cycles at the 180 percent load step; it failed aft er a total of 2.5 million cycles.
PI POTENTIAL
Sharp believes the 3TEX-tested Pi joint design could reduce the weight, cost and need for repairs in wind blades. “By increasing the ultimate strength and fatigue life, this type of joint should permit designers to reduce the material in the loaded sections of the blade, lowering material and manufacturing costs.” Indeed, 80m to 100m (262-ft to 328-ft ) long blades now under development for off shore turbines might soon benefi t from Pi joints (see “Learn More”).
Further, integrating Pi joints into blade construction methods appears to be a solution because increasing blade lengths tests the limits of current bond technology. During their discussion of de-sign drivers and expected failure modes in future longer blades at the 2012 Sandia Wind Turbine Workshop (May 31-June 1, San-dia National Laboratories, Albuquerque, N.M.), representatives of Bladena (Ringsted, Denmark) pointed out that when the blade length surpasses 60m/197 ft , fatigue failure in the bondlines and failure of the shear web become a critical failure mode, a reality that could be addressed with Pi joints. Bladena, a commercial spin-off of wind energy research institute Risø DTU (Roskilde County, Denmark), also observed a nonlinear crushing pressure phenom-enon that increases in longer blades because they bend more. Th e Pi-jointed beams in the test blades exhibited increased stiff ness, which would counter the crushing pressure. Finally, Bladena iden-
tifi ed interlaminar failure in the load-carrying spar caps and shear web fl anges as a risk that increases with blade length. Orthogonally woven 3-D textiles are inherently resistant to delamination. Th us, they could improve performance not only in the shear web-to-blade shell joint but also in the spar cap. Th erefore, Sharp believes Pi joint preforms could provide benefi ts elsewhere, especially in very large composite structures, such as those in ships. | CT |
Work in Progress
reforms have been used for almost 80 years in infusion molding processes. For most of that history, however, the vast majority were made with chopped glass fi bers
directed over perforated metal forms in vacuum-forming processes — think molded transit bus seats, for example. More recently, engineered preforms have been developed through the use of automated knitting and weaving machinery. Th ese two- and three-dimensional constructions are increasingly capable of reinforcing high-performance structural composite parts, but most have failed to enter the manufacturing mainstream in the automotive industry due to their perceived high cost, the auto
industry’s change-averse culture and some diffi cult-to-surmount engineering hurdles.
During the past decade, however, more stringent fuel economy and emissions standards have overcome automakers’ resistance to change. Many are developing structural composites in mass-pro-duced vehicles for weight reduction on the strength of recently devel-oped rapid infusion processes designed to meet high auto build rates. Th e good news is that equally fast, cost-eff ective and sophisticated engineered preform technologies are being developed in parallel.
“Preforms can be created faster than metal can be stamped, on the order of several seconds,” asserts Dan Buckley, manager of re-search and development at American GFM Corp. (AGFM, Chesa-peake, Va.). “And contrary to what many in the industry think, pre-forming can save money when creating parts,” he continues. As a new generation of engineers comes of age, its members are circling back to the concept of assembling a complex part’s continuous fi ber reinforcements in a separate, automated process as a way to acceler-ate composite part processing — with the goal of meeting the auto industry’s part-per-minute production rate.
Not yet in full production, with one
exception, all are aimed at accelerating
composite part manufacture at fast
automotive rates.
STRUCTURAL PREFORM STRUCTURAL PREFORM TECHNOLOGIES TECHNOLOGIES
EMERGE FROM THE SHADOWSEMERGE FROM THE SHADOWS
This automated PreformCenter work cell designed and built by
Dieffenbacher GmbH (Eppingen, Germany) has the capability of
producing preforms at production-rate cycle time (less than
three minutes), using a cutting table, robot arm, binder
application module and draping module. The image below shows
a demonstration preform produced by the work cell.
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FEATURE: Automotive Composites
BACK TO BASICS
To review, a preform is a preshaped fi ber form. Its fi bers are arranged in one, two or three dimensions in the approximate shape, contour and thickness desired in the fi nished composite part. Tradition-ally, preforms are made in a separate mold and shaping process, not in the fi nal part mold. Preforms can be made by spraying discrete chopped fi bers combined with a binder over a form; by stacking tackifi ed continuous fabric plies; by weaving, braiding or knitting shapes, or stitching continuous fi ber materials; or even by combining several types of continuous reinforcements (see “Learn More,” p. 29). Although preforms can be made of prepreg (see “Prepreg preforms for high-rate automotive apps” under “Learn More”), the vast majority are dry fi ber forms that are subse-quently impregnated with resin in a closed mold process, such as resin transfer molding (RTM) or vacuum-assisted resin transfer molding (VARTM). Newer, nontraditional preforming concepts that combine thermoplastic tapes and mats are now in the mix as well, and several suppliers, including Sigmatex High Technology Fabrics (Benicia, Calif.), now off er roll goods with integrally woven three-dimensional structure.
No matter the process, dry preforming fi xes the fi bers in de-sired orientations, at a predictable fi ber volume, and minimizes the hands-on labor required for layup, says Buckley: “It allows you to better achieve a net-shape part, provides uniformity, part to part, and makes the molding process more effi cient with the shortest pos-sible mold open time.”
Th e preform type depends on the need. Chopped fi ber preforms with randomly oriented fi bers have isotropic properties. Although it is possible to adjust a spray pattern in a way that aligns and orients fi bers to some degree, the load-bearing properties of such preforms are generally limited by the short fi ber length. For better part prop-erties, continuous fi bers are called for, and preforming for high-performance structures typically involves engineering fabrics, such as multiaxials.
FORMING A UNIFORM PREFORM
Today preforms can be quite complex, a fact that multiplies processing challenges. For example, fabrics must be manipulated to the desired preform shape, but because glass and carbon fi bers don’t stretch, fi ber breakage can cause problems. Conformability, or drap-ability — how well the fi bers of a multilayer fabric shear and change position during shaping, without losing continuity — depends on the fabric type, stitch density, stitch tightness, roving or tow density and whether additional materials (e.g., mats) are added to the preform. “During the preforming process, fi ber orientations change, which changes the local fi ber density and thickness,” explains Buckley. “Failure to conform to the preform tool creates numerous process and performance problems.” Determining conformability is a key issue during preform process design.
“Th e trend toward production of complex automotive parts requires noncrimp engineering fabrics for effi ciency, but unantici-pated fi ber shift s during shaping can cause gaps and misalignment,” adds Ulrich Moerschel of textile testing instrument developer Tex-techno (Mönchengladbach, Germany). His fi rm has developed a way to detect conformability problems with the recent introduc-
tion of DRAPETEST, an automated drapability tester, which won a JEC Innovation Award in 2012. To simulate fabric stress during preforming, a motor-driven piston moves upward through a fl at circular fabric sample, and the force needed to deform the fabric is measured. A camera, with appropriate illumination, photographs the sample at intervals during the piston’s travel while the entire sample is rotated so technicians can inspect the surface for gaps and fi ber loops or breakage. An optional triangulation sensor is available to detect larger-scale defects, such as wrinkles, Moerschel explains. Deformation data and images are displayed on a computer, and im-age analysis technology developed at the Faserinstitut Bremen (FI-BRE, Bremen, Germany) enables automatic fabric fault detection. DRAPETEST is based on an earlier prototype developed by multi-axial manufacturer SAERTEX GmbH & Co. (Saerbeck, Germany) under a research program funded by the German government. “Th e tester gives manufacturers a chance to detect problems like thicken-ing, creasing or bunching in a multiaxial fabric before the reinforce-ments are included in a preforming program,” adds Moerschel.
Springback also can cause problems, cautions Buckley. When an engineering fabric is subjected to pressure in the preforming
hbansi
wisfi arerp
STRUCTURAL PREFORM TECHNOLOGIES
EMERGE FROM THE SHADOWS
Visible in these samples are the wrinkles, bunching and even fi ber
breakage that can occur when multiaxial fabrics for preforms are
manipulated and stressed during preforming. Testing is needed to
determine how “conformable” a fabric is or how easily a fabric can be
draped during the preforming process. .
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press, it causes areas of high fi ber stress, he explains. Th ose fi bers have a tendency to relax, or spring back, to relieve the stress, which results in an improperly sized preform. “Th e preform tooling must be designed to compensate for springback, and achieve ‘overform-ing,’” he says. Overforming refers to pressing the fabric beyond the actual part dimensions in deep draw areas, on the order of a few millimeters, so that when the preform springs back slightly, it con-forms to the desired part dimensions. “Th is is why you should not make preforms in the actual part molding tool,” Buckley advises.
“When springback occurs — because the tool isn’t optimized for overforming — the preform will be too small.”
Another big consideration is ensuring that the material used to bind or hold the preform in place during the forming process is compatible both with the sizing used on the fi bers and the resin that will infuse them. Reported problems include thermoplastic bind-ers that repel thermoset molding resins, resulting in weak resin/fi -ber bonds, and binders that “wash” and rise to the preform surface when it is inserted in a hot tool, causing fi nished part defects. In recent years binder suppliers have developed binders that crosslink and cure with the matrix resin. AGFM off ers thermoset binders, for example, designed to work with fi ber sizings and to be chemically compatible with thermoset molding resins.
MACHINE AND PROCESS REFINEMENT
Equipment and materials suppliers have spent many years devel-oping a variety of preforming methods. AGFM, for one, off ers its fast CompForm process, which employs a proprietary light-curable binder. Billed as curable in less than 20 seconds, the binder, claims Buckley, has the potential to cure as quickly as one second, if the preform shape and complexity permits. Th e binder works on opti-cally transparent materials, such as fi berglass engineering fabrics and mats, and it can even cure through some lightweight foams and hybrid glass/carbon materials.
Th e binder is produced by Zeon Technologies Inc. (Salisbury, N.C.) and consists of a resin backbone that can be functionalized
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A preform demonstrator part is
shown in the mold (above), after
shaping by a forming template.
The photo at right shows the
preform, held in shape by a light-
curable binder, after it was
shuttled into position under high-
intensity lamps, to cure in 17
seconds, well within automotive
part production cycle times.
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FEATURE: Automotive Composites
North Coast Composites delivers the complete parts solution. For 35 years North Coast Tool & Mold has been an industry leader in the manufacture of molds for high performance composites.
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for compatibility with a wide variety of matrix resins; in addition to the photoinitiator additive, a viscosity reducer is added to accelerate wetout. Light from 6,000W visible lamps, such as those provided by Heraeus Noblelight Fusion UV Inc. (Gaithersburg, Md.), at a wave-length of 400 to 430 nm, sets the shape. Low-energy light-emitting diode (LED) lights are also options as light sources, says Buckley. Because the binder requires no heat to cure, simple, low-cost tooling can be employed, without internal or external heating and cooling channels and controls. Although the high-intensity, instant-on cur-ing lamps can be expensive, they off er a long working life, and the short cure cycles ensure that the per-part energy cost is low.
A recent prototyping project involved the front bumper for a pro-duction car using a biaxial hybrid glass fi ber/carbon fi ber fabric. Th e fabric was layed in a female preform tool situated on a shuttle table; the shuttle then transferred the tool into position under a matching air-controlled “forming template” that compressed the layup from above. Aft er shaping, the shuttle moved the tool to a third position, directly under an array of three high-intensity lamps, for a cure that took approximately 17 seconds. Buckley explains that the amount of binder can be varied across the preform, and individual lamps within the light source can be aimed at specifi c areas of the preform to op-timize local stiff ness. It is also possible to add customized surface fi nishes by inserting thermoformed skins into the preform molds, backing them with prepreg, and then molding the part.
AGFM says it can design preforming machines with molds and shuttles to meet the production needs for any size of preform. Fur-ther, CompForm can be modifi ed to accom-modate opaque carbon fi ber-reinforced ma-terials, reports Buckley, through the use of a newly developed two-part, quasi-anaerobic binder, also available from Zeon, that cures by removing reaction inhibition chemistry with vacuum and heat.
Preform R&D has been underway for years at the Institut für Textiltechnik (ITA) at RWTH Aachen University (Aachen, Germa-ny), notes Christoph Greb, the deputy of ITA’s Composites Div. His group has delved deeply into the economics of preforming and how various approaches will impact a part’s pro-duction cost. “Composites off er great poten-tial to reduce automotive structural weight, yet they’re currently not economically com-petitive with conventional materials, from a production point of view, due to the manual or semi-automated labor involved,” he says. ITA’s approach is to combine automated pro-cesses to achieve an economically viable pro-duction process at its ITA-Preformcenter.
Greb explains that ITA has developed a wide range of automated preforming tech-nologies, and their applicability to large-scale auto production was recently validated by way of a complex carbon fi ber/epoxy demonstration part: a 48-inch by 29-inch
(1,230 mm by 760 mm) composite roof segment that could replace the portion of the current steel roof that slides backward and stows in the trunk of the BMW 3 Series convertible.
For the demonstration project, ITA used a multiaxial weft in-sertion machine, manufactured by LIBA Maschinenfabrik GmbH (Naila, Germany) to make a multiaxial noncrimp fabric (NCF) specifi c to the part. Th e machine was modifi ed to change the fabric thickness locally, add z-directional reinforcements, create cutouts and affi x additional fabrics and mats. Th e result is a process that can create, on the fl y, a near-net shape that exactly matches the preform requirements — what Greb calls a “tailored NCF.”
“If a complete preform can’t be created in a single step on the LIBA machine, then additional automated machines are needed,” explains Greb, adding, “In this case, we wanted to integrate fastener inserts and stringers, so we went to a multistep preforming process.” A second work cell was outfi tted with a CNC cutting table, supplied by Assyst Bullmer Spezialmaschinen GmbH (Mehrstetten, Ger-many), and an industrial robot arm from KUKA Roboter GmbH (Augsburg, Germany), with the appropriate end-eff ector. Th e work cell cuts, assembles and places six foam-cored stringers and multiple monolithic padups with embedded aluminum fasteners onto the tailored NCF laminate, with a heat-activated thermoplastic binder.
ITA then evaluated the economic feasibility of such a multistep preforming cell and process as if it were implemented in a produc-tion setting. An in-house soft ware tool, EcoPreform, was used to virtually construct the preforms and project labor and material
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costs. Assumptions included 10-year linear depreciation of all ma-chinery. Greb points out that material costs make up about 95 per-cent of a preform like the one used for the BMW roof demonstrator. Th at said, the data showed that a preform based on a tailored NCF made by the LIBA machine coupled with robotic placement is much more effi cient to produce than a single-step preform, but because
it requires more capital equipment, the per-piece cost is about the same. However, the analysis also proved that as the part production rate increases, the unit cost of the preform goes down.
Although no projects are yet in production with an OEM, Greb notes, “We are constantly working on further improving the process by enhancing both single- and multi-process chains.”
A MULTISTEP PREFORM CELL
In 2011, the Fraunhofer Institute for Chemical Technology (ICT, Pfi nztal, Germany) began a long-term collaboration with the University of Western Ontario (London, Ontario, Canada). Th e Fraunhofer Project Centre for Composites Research at Western
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Outer shell
Reinforcements
Stiffeners
Inserts
760 mm (29 inches)
This demonstration composite auto roof component, developed by the
Institut fur Textiltechnik (ITA) at the RWTH Aachen University, was
produced in a multistep automated process that produced a tailored
noncrimp fabric, then robotically formed and placed the foam-fi lled
stringers and metallic fasteners.
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FEATURE: Automotive Composites
opened its doors in November 2012 to develop preforming processes, reports Vanja Ugresic, a Centre research engineer. A key element will be a fully automated PreformCenter, designed by Dieff enbacher GmbH (Eppingen, Germany, and Windsor, Ontario, Canada) and slated to be up and running in early 2014.
According to Dieff enbacher’s Matthias Graf, managing director of the Business Unit Forming, the goal for the PreformCenter is a less than three-minute process cycle, from the unwinding of fabrics to the fi nished net-shape preform, syncing the preform cycle time to the mold cycle time.
Th e PreformCenter comprises several modules: the fi rst is a CNC cutting table — more than one table can be included as the project grows — to cut the plies necessary to make the part preform. “We use a roll knife, which we believe causes less drag and thus no fi ber disorien-tation,” explains Graf. A robot arm equipped with a vacuum pick-and-place end-eff ector then transfers the cut plies from the cutting table to the binder application module, a cabinet containing spray equipment with nozzles that spray an epoxy-based binder upward onto the pre-form’s bottom surface. Although the binder is characterized by ther-moplastic behavior, it is reportedly compatible with the part resin.
Th e robotic arm moves the individual plies back and forth to direct the binder where needed and, Ugresic explains, “As part of the Cen-tre’s research, we will optimize the binder dosing to achieve the lowest amount of binder possible, on the order of about 3 percent of preform weight, to minimize any eff ect of binder on the part quality.” Th e ro-bot then places the tacky laminate stack on a “draping” module,
which automatically forms the 2-D layup into a 3-D shape — the most challenging step of the process. Although Dieff enbacher won’t release specifi c details about the draping and forming methodol-ogy at this point, Graf revealed that aft er considerable research and modeling, “we are able to minimize fi ber stress during the preform-ing shaping, and control and infl uence fi ber orientation with our system.” Th is, he says, has eliminated preform wrinkling without sacrifi cing cycle time.
Ugresic adds that a rigid, heated lower form with an “adaptive” upper mold shapes the preform at a low compression force. Th e ap-plied heat ranges from 80°C to 120°C (175°F to 248°F), depending on the binder. “Achieving wrinkle-free preforms regardless of ma-terials used will be a strong R&D focus at the Centre,” she asserts.
Aft er the PreformCenter is up and running, the Fraunhofer Project Centre for Composites Research will be available to auto-motive customers who are interested in trialing preform methods and materials, says Ugresic. “We are open to cooperate with auto-motive OEMs, and strategic alliances are already under evaluation. Depending on the complexity of the project, Dieff enbacher may be involved as a development partner.”
OVERMOLDING CONTINUOUS REINFORCEMENT
A fi ve-year-old startup, EELCEE AB (Trollhättan, Sweden, and Lausanne, Switzerland), is marketing a uniquely diff erent approach to preforms. An automated process cell pulls multiple continuous fi ber rovings or tows from a creel through a series of dies that wet
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When processing composite material, successful removal from the mold is critical to achieving higher quality, lower cost and boosted operational efficiency.
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out the fi ber with resin. Th en, a robotically controlled layup head creates an open, tailored 3-D “skeleton,” trademarked QEE-FORM, by rapidly placing the fi ber/resin strands, in any shape or size, around integral metallic bushings or fastener points. Th e resulting QEE-FORM frame is then robotically placed in either an injec-tion molding machine, where it is overmolded with thermoplastic resin, or in a compression molding press, where it provides addi-
tional reinforcement for glass mat thermoplastic (GMT) or sheet molding compound (SMC). “Our integrated preform processing technology, trademarked QEE-TECH, enables the production of lightweight, structural thermoplastic composite parts at a high rate and at lower cost than legacy materials,” claims company founder Dr. Jan-Anders Månson. “Th e tailored preforms allow a shorter and faster path from fi ber and polymer to fi nished parts.” Cycle time is 45 to 90 seconds, in the range of the part forming process that follows. Woven or unidirectional fabrics, in prepregged form, can be incorporated into the QEE-FORM preform and easily fi xed in place with an application of heat, with tailored structural properties.
“Th is technology integrates the advantages of conventional ther-moplastic and compression molding along with those of continu-ous fi ber reinforcements,” Månson sums up. Targeted applications include structurally loaded auto parts, such as bumper beams, seat structures and front-end module carriers. EELCEE develops a con-cept and design in consultation with the OEM or end-user, then produces the QEE-FORMs at its production facilities.
COMPLEX PREFORMS ENTER PRODUCTION
Automakers have fi nally begun to take notice. EELCEE won a JEC Innovation Award at the 2013 JEC Asia event in Singapore for its work with Hyundai-KIA Motor Group and molder Hanwha (both based in Seoul, South Korea) on a new thermoplastic bumper system. A 3-D QEE-TECH tow framework is overmolded with GMT in a compression molding process. “Th e QEE-TECH applica-
A radical and rapid preforming approach developed by EELCEE AB
(Trollhättan, Sweden) uses fi ber tows or rovings that are robotically slung
around a number of fastener points. The resulting skeleton or frame (shown
in white) is then robotically transferred to an injection or compression
molding cell for overmolding with thermoplastic material. The process is
being adopted by automaker Hyundai-KIA for production bumpers.
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FEATURE: Automotive Composites
Read this article online | http://short.compositesworld.com/Mqzr7Fg7.
Read “Prepreg preforms for high-rate automotive apps”online | http://short.compositesworld.com/PSmJC7Ex.
See previous CT coverage of preforming technologies in the following:
“High-volume preforming for automotive application” | CT October 2008 (p. 52) | http://short.compositesworld.com/3QQtyZX7.
CT’s sister publication High-Performance Composites has examined preform approaches within the past year in the following:
“Tailored Fiber Placement: Besting metal in volume production” | HPC September 2013 (p. 54) | http://short.compositesworld.com/7QEhsvZ0.
“Rapid layup: New 3-D preform technology” | HPC September 2012 (p. 40) | http://short.compositesworld.com/BtNTN2jN.
Technical EditorSara Black is CT’s technical editor and has served on the CT staff for 14 [email protected]
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tions are, in general, about 30 percent lighter and nearly 20 percent less costly than the legacy metallic version and off er much better collision performance,” says Månson. Th e joint development began in 2010, with the design based on modeling, simulation and full prototype testing. Th e bumper meets the Insurance Institute for Highway Safety (IIHS) 10 kmh (6.2 mph) full barrier requirement and is slated to launch on two passenger car models in 2014.
Another award-winner is the Part via Preform (PvP) process developed by Toho Tenax Europe GmbH (Wuppertal, Germany), which won an AVK Innovation Award at Composites Europe 2013. Th e one-step “bobbin to preform” process uses Tenax carbon fi -ber combined with a binder resin to form a “binder yarn,” which is chopped in an automated process and combined with UD car-bon tapes to form complex preforms for high-pressure resin trans-fer molding, achieving an acceptable tradeoff between mechanical properties and cost, says the company.
Elsewhere, BMW (Munich, Germany) has put in place perhaps the most complex preforming process to date: the automated pre-form lines at its Dingolfi ng and Leipzig plants are currently produc-ing the all-carbon Life Module body for the i3 electric car. Carbon multiaxial fabrics with binder are preformed in a multistep process. Th e fabrics are assembled in Wackersdorf, Germany, from carbon fi bers produced at its Moses Lake, Wash., facility operated by SGL Automotive Carbon Fibers (a joint venture between BMW and Weisbaden, Germany-based SGL Group). According to published sources, the Life Module comprises 150 separate pieces that are preformed, with heat (in some cases, ultrasonic energy) to set the binder, and then resin transfer molded in a high-pressure press.
Concludes Buckley, “Preforming is extremely underappreciated. It’s actually more important than the molding process, but it has so oft en been overlooked.” Given the current auto lightweighting push, new preform technologies appear to be reaching maturity. | CT |
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FEATURE: Wind Energy Update
he past year was exceptional for the world wind energy market, as wind-generated electricity continued to increase its share of the overall electric power supply base. Th e global
wind power industry grew about 16 percent in 2012, adding 45 GW of new capacity. Th is increased total capacity to 285 GW, or about 2.62 percent of the world’s electricity, according to statistics published by online energy market news aggregator Th eEnergy-Collective.com. In the U.S., 6 GW of new capacity was installed in 2012, 19 percent more than in 2011. Wind turbines now account for roughly 3.4 percent of all electricity generated in the U.S. With the Jan. 1, 2013, extension of the federal Production Tax Credit, the U.S. is expected to add 5 GW of wind-generated electricity this year.
Despite the ongoing expansion of wind power, the wind energy industry’s mandate to innovate has never been greater. Its ability to compete with other renewable and nonrenewable sources of energy and the continued growth and profi tability of turbine manufactur-ers and suppliers depend on it. Areas of concern include better ways to enhance not only the mechanical and aerodynamic performance of turbine blades but also their weatherability and resistance to envi-ronmental elements. It is also incumbent on the industry to explore ways to reduce the radar signature of wind farms — an issue that has resulted in delays or cancellations of some farm installations. Last, there is a sense of urgency about mitigating the cost of manufactur-ing, installing and metering wind turbines in anticipation of what
many experts predict will inevitably be a subsidy-free, level energy playing fi eld.
PUSHING PAST THE
EFFICIENCY PLATEAU
If the rotors of a wind turbine are not turning, the turbine is not producing electricity and its owners are not making money. Th at fact feeds the perception among critics that wind cannot compete with on-demand power sources, such as fossil fuels, nuclear and hydro. Th us, one rationale for longer rotor blades is that the longer the blade, the greater the amount of time a turbine will spend in service under variable wind conditions, a metric known as capacity factor.
Despite double-digit wind energy industry growth, turbine blade manufacturers and
materials suppliers acknowledge a pressing need to reduce costs and innovate.
T
PROGRESS &CHALLENGES
Wind Blades
Pictured here is one-half of the mold
Siemens AG (Erlangen, Germany) is using to
build rotor blades for what the company says
will be the world’s largest turbine, the SWT-
6.0-154. Its 75m/246-ft balsa-cored glass/
epoxy blades will be molded in one piece to
eliminate seams and bonded joints. A Danish
energy provider is planning to install about
300 of the turbines off the British coast when
testing is complete.
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Keith Longtin, general manager, wind product line, for GE’s renewable energy business, says the company has increased the capacity factor of its current turbines to more than 50 percent, up from roughly 35 percent 10 years ago. Longtin reports that GE sold more than 1,000 of its 100m/328-ft diameter 1.6-MW 1.6-100 wind turbines in 2012 — all installed in the U.S. Th is turbine has a capacity factor of roughly 53 percent. Th e turbine’s 48.7m/159.8-ft blades are E-glass/epoxy sandwich constructions with a hybrid core that comprises balsa wood and PVC and SAN foams. Each blade weighs approximately 10 metric tonnes (22,000 lb), has a root diameter of 2.5m/8.2 ft and a chord width of 3.5m/11.5 ft .
More recently, Invenergy (Chicago, Ill.) became the fi rst com-pany to purchase GE’s new 2.5-120 series turbine. Th e turbine is equipped with 60m/197-ft long blades and has a capacity factor of more than 50 percent in low-wind conditions. Invenergy purchased three of the 2.5-MW turbines, which will be installed as part of Goldthwaite Energy Center, an 86-turbine facility under construc-tion in Mills County, Texas. GE says the turbine is the fi rst to in-tegrate short-term battery storage and soft ware that enables power producers to store short-term surges in power during peak wind conditions. Th is onboard system eliminates the need for more costly offl ine, farm-level battery storage systems.
Longtin reports that one of the company’s strategies for reduc-ing variability and costs in the ramp up to bigger blades is a stan-dardized design and manufacturing process, which facilitates scal-ability of composite layups. Th e company also collaborates with its suppliers to fi nd ways to enhance automation. For example, one of the company’s suppliers, TPI Composites, which manufactures ro-tor blades for GE’s turbines at its plant in Newton, Iowa, reports using hydraulic power hinges to assemble blade halves. Th e hinges have eliminated the need for fl ip fi xtures for skin demolding, result-ing in signifi cant reductions in assembly time. TPI manufactures blades using the Seamann Composites (Gulfport, Miss.) Resin Infu-sion Molding Process (SCRIMP), in which feed lines, vacuum lines and embossed distribution channels are integrated into a reusable vacuum bag to reduce setup time and improve process repeatability.
BETTER DESIGN AND
DESIGN FOR MANUFACTURE
Building ever-larger rotor blades using the same or similar produc-tion methods and materials is a strategy now subject to the law of diminishing returns: Th e increase in the weight of, and loads borne by, longer turbine blades outpaces the increases in power capacity. Turbine manufacturers, therefore, are vigorously investigating opti-mized designs, lighter materials and more effi cient manufacturing processes to reduce blade weight and cost.
Chicago, Ill.-based Invenergy is installing three of
GE’s new 2.5-120 turbines at the Goldthwaite Wind
Energy facility presently under construction in Mills
County, Texas. The largest in GE’s line, they feature wind
blades 60m/197-ft long and a new, onboard short-term
battery storage system, which enables energy storage
during peak generation.
Custom molder Molded Fiberglass Cos. (Ashtabula, Ohio) manufactures
spinner nosecones, which fi t over the rotor hub, by vacuum infusion from
E-glass and polyester. Company VP Carl LaFrance says greater collaboration
between suppliers and blade manufacturers is a must if the industry is to
reduce system costs and compete with other sources of power.
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FEATURE: Wind Energy Update
chase and install about 300 SWT-6.0-154 turbines off the British coast, according to a recent press release from Siemens.
Meanwhile, Kolding, Denmark-based LM Wind Power’s 73.5m/240-ft blades were installed on Alstom’s (Levallois-Perret, France) Haliade 150-6MW wind turbine in Carnet, France, this past year, and the company has plans to open a blade manufacturing plant in Cherbourg, France, and begin production of the blades there by 2016 (see “Learn More,” p. 35). Th e glass/polyester blades feature the company’s SuperRoot design, which supports blades that are up to 20 percent longer without an increase in root diameter. Addition-ally, in 2012, LM Wind Power extended its GloBlade line of ultraslim wind turbine blades to 3-MW turbines. Originally introduced for the 1.5-MW segment, the GloBlade replacement blades are designed with “plug-and-play” features that make them compatible with a va-riety of turbine platforms and aerodynamic confi gurations. Th e new 3-MW line includes 58.7m and 61.2m (192.6-ft and 200.8-ft ) blades, which the company says can improve annual energy production by as much as 14 percent, compared to the standard blades they replace.
Molded Fiber Glass Cos. (MFG, Ashtabula, Ohio) custom molds blades and a variety of parts for wind turbines. For example, the
A potential paradigm shift in wind turbine blade manufacture is afoot at
GE Wind Energy (Niskayuna, N.Y.). The company’s global research arm,
along with Virginia Polytechnic Institute & State University (Blacksburg,
Va.) and the National Renewable Energy Laboratory (Golden, Colo.), re-
cently secured a three-year grant under the U.S. Department of Energy’s
Advanced Research Projects Agency to investigate the use of resin-
impregnated architectural fabrics as a substitute for conventional com-
posite laminates in the construction of wind blade skins. In this design,
as envisioned, fabric is stretched or “tensioned” around a spaceframe of
stamped metal ribs.
The fabric is impregnated
with resin to make it impermeable
to wind and water intrusion. Wen-
dy Lin, GE’s principal engineer
and lead on the project, declines
to identify the fabric; however,
she stresses that the resin is nei-
ther an epoxy nor a polyester, but
a “rubbery,” compliant material
that allows GE to assemble the
blade in large segments without risk of the blade buckling.
Lin says the impetus for the project was an internal directive at GE
to reduce the cost of manufacturing wind blades by 50 percent. If the
fabric is successful, GE claims the new blade design could reduce blade
production costs by up to 40 percent and put wind energy on equal
economic footing with fossil fuels, without government subsidies. Lin
says the design would permit automotive-type precision and tolerances
and eliminate the logistical problem, and associated costs, of transport-
ing long blades to turbine sites. Instead, the blade components could be
shipped in container kits and assembled on site. “We still have a ways
to go to prove it out, however,” Lin admits. “Size constraints imposed by
current technology require thinking outside the box.” But, she says, the
concept could pave the way for blades as long as 130m/426.5 ft, mak-
ing them suitable for harvesting wind in moderate wind locales.
A DIFFERENT TYPE OF BLADE?
Wendy Lin, a principal engineer
at GE Global Research, wraps resin-
impregnated fabric around a proto-
type wind blade segment. The in-
spiration for GE’s tensioned-fabric
concept was a similar fabric used as
the cover of an outdoor café (left) at
GE’s John F. Welch Technology Center
in Bangalore, India.
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Siemens AG (Erlangen, Germany) is building what is purported to be the world’s largest wind turbine, the SWT-6.0-154. Each of its three B75 blades measures about 75m/246 ft in length. Fabricated as a single cast part, comprising glass, epoxy and balsa wood, the blade is molded via the company’s patented and trademarked Inte-gralBlade process. Th e seamless blade has no bonded joints — weak points that could crack or separate, exposing the joint to water in-gress and accelerated weathering. Additionally, a weight savings of about 20 percent, compared to conventionally produced blades, is achieved by incorporating a specially designed blade profi le, shaped to maximize the rotor capacity factor at a variety of wind speeds. Th e turbine has a cut-in wind speed of 3 to 5 m/sec, produces nominal power at 12 to 24 m/sec and has a cut-out wind speed of 25 m/sec. It is part of the company’s D6 platform, which replaces the gearbox, coupling and generator with direct-drive technology that eliminates about 50 percent of wear-prone and geared parts. Th e reduction in associated maintenance costs is especially advantageous for off shore applications. Siemens is testing the B75 blades on a prototype 6-MW turbine at Denmark’s Osterlid test station. Aft er testing is complete, power supplier Dong Energy (Fredericia, Denmark) plans to pur-
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company manufactures a spinner nose cone, which fi ts over the windward side of the rotor hub, from E-glass fabric and polyester for a major wind turbine manufacturer. Carl LaFrance, MFG’s VP of re-newable energy products, cites the need to reduce wind energy’s cost per kW-hr and to make investments in material and process R&D. “We don’t have a full understanding of how blade design, materi-als and manufacturing processes aff ect system costs,” says LaFrance, “so we don’t have any idea about how much cost we could potential-ly take out.” He believes that will require more upfront collaboration between custom molders and turbine manufacturers, but adds, “it’s a conversation not all customers are willing to have because of the competitive nature of this business.”
LaFrance specifi cally earmarks the need for tougher matrices, and he notes that early testing and prototype work with polyurethanes appears promising. “Poly-urethanes have much better fatigue prop-erties than either polyester or epoxy,” he contends. LaFrance also reports that some materials suppliers are researching meth-ods to make vinyl ester a tougher material.
EROSION CONTROL
AND DE-ICING CAPABILITY
As blades get longer and blade tips reach greater speeds, resistance to wind-driven rain, ice, sand and salt is a key performance criterion, especially along the blade’s leading edge. When wind-driven particulate strikes a blade spinning as fast as 60 m/sec, there is the potential for damaging shear forces in the fi rst laminate layer of the edge. Leading-edge erosion reduces power output, which results in signifi cant revenue loss for wind farm operators.
To counteract erosion, LM Wind Power recently introduced a new protective coat-ing technology, LM ProBlade Collision Barrier. Th e company claims the coating can improve erosion resistance along the leading edge by up to 20 times, compared to standard barrier coatings already in use. Th e coating system comprises a primer and an aliphatic-based, solvent-free, two-component, highly elastic polyurethane topcoat. LM says results of independent testing on prototype blades shows the coat-ing lasts about twice as long as leading-edge thermoplastic polyurethane tape. Tape pro-duces aerodynamic drag, and LM estimates that eliminating it can enhance the average annual energy production of a turbine by 2 percent. Th e company began serial produc-tion of the coating in the second quarter of 2013. Lene Ri Ran Kristiansen, manager of
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global communications at LM, says the barrier technology will be available, initially, only on blades produced by LM Wind Power.
Another option, Arkema Inc.’s (King of Prussia, Pa.) KYNAR PVDF-acrylic hybrid emulsion coating, has been used for more than 30 years as an architectural weather coating on exposed metal in large commercial buildings and public structures. Th e original solvent-borne emulsion requires baking at temperatures up to 200°C/392°F to cure. However, the company introduced a water-based version of KYNAR, in both thermoplastic and thermoset for-mulations, which is curable at room temperature and can be applied to a variety of composites.
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FEATURE: Wind Energy Update
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Th e standard rain erosion test, fi rst developed for helicopter blades, spins blades on a fi xture at a high speed through simulated rain. Th is test is very expensive. Arkema, therefore, is working with NDSU to develop an alternative test method that keeps the part sta-tionary and uses a wind tunnel to accelerate water droplets into the part at high speed. Th is method will be used to test the rain erosion of blades coated with KYNAR-based paints. Th e company will be presenting preliminary test results at several wind energy conferenc-es this year. Wood says the company also has done studies that sug-gest the hybrid resin may have superior long-term erosion-resistance and ice-shedding properties compared to a number of commercial
urethane coatings that are currently in use.To address leading-edge erosion, 3M’s
Renewable Energy Div. (St. Paul, Minn.) now off ers Wind Blade Protection Coat-ing W4600. Th e product, which was intro-duced to the market in May, is a two-com-ponent polyurethane coating designed for application via brush or by casting at the OEM facility. 3M also off ers Wind Tape 8608 and 8609 for erosion control at the leading edge. Th e pressure-sensitive tape is UV stable and puncture resistant, and it can be die- or plotter-cut to conform to complex 3-D shapes.
Currently GE Wind Energy employs process controllers on most of its wind tur-bines to manage ice buildup on the turbines’ rotor blades. When the controller detects imbalances in the rotor as a result of ice buildup, it adjusts the rotor speed to allow continued safe operation, or it shuts down the turbine if ice buildup becomes too ex-treme. But Longtin reports that GE also has conducted fi eld testing of a “nanoparticle, ice-phobic coating” on its 1.6-MW turbine blades, with encouraging results. “We are going to announce the results later this year but we think the technology has promise,” says Longtin.
REDUCING WIND TURBINE
RADAR INTERFERENCE
As wind farms proliferate, a concern about turbine radar interference has, in recent years, prompted aviation, weather, military and marine operations to contest proposed wind turbine installations. Th e Union of Concerned Scientists (Cambridge, Mass.) estimates the issue has delayed the instal-lation of as much as 6 to 9 GW of poten-tial wind energy production. In a white paper that addresses radar interference from wind farms, the group recommends a number of mitigation measures, including
Kurt Wood, group leader of KYNAR PVDF coatings R&D, reports that the company has been working with researchers at North Dakota State University (NDSU) to evaluate the performance of paints formu-lated with the water-based thermoset and a hybrid resin when they are applied on typical glass/epoxy laminates as a possible all-purpose lead-ing-edge and weather-resistant coating. In the thermoset formulation, hydroxy-functional monomers are incorporated in the acrylic portion; the hybrid resin is combined with commercially available water-dis-persible polyisocyanate crosslinkers to produce a two-part urethane. Th e resulting crosslinked polymer in the applied coating is structured as a bi-continuous network of fl uoropolymer and acrylic urethane.
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upgrades to the aging, long-range radar infrastructure, modifi ca-tions to wind farm design to reduce radar cross-section and the use of “gap fi llers” in radar coverage.
Turbine manufactures also are investigating technologies to re-duce the intrinsic radar signature of wind blades. Vestas Wind Sys-tems A/S (Aarhus, Denmark) is reportedly researching the use of a stealth technology, similar to what is used in military aircraft , to reduce a turbine’s radar signature. Th e company has built a num-ber of experimental wind blades that comprise two layers of glass fabric printed with a special “ink.” Th e radar signal passes through the fi rst layer and is eff ectively trapped between the two layers. Ac-cording to online reports, the technology works, but the cost could be prohibitive — especially considering the market pressure on turbine manufacturers to reduce, not raise, costs. Further, a turbine completely undetectable to radar would pose a hazard to aircraft fl ying in the vicinity of a wind farm. Th e trick, which Vestas is attempting to master, is to “tune” the technology so a spinning turbine doesn’t appear as a threat on the aircraft ’s radar, yet doesn’t entirely disappear from the radar screen.
Elsewhere, GE Wind Energy is taking a slightly diff erent approach to reduce a tur-bine’s radar interference. Longtin reports that GE’s R&D center in Munich, Germa-ny, has investigated applying a number of “commercial radar-absorbing materials” to rotor blades, which have subsequently been tested on turbines and were shown to be capable of reducing radar interference. “We are using materials that you can pur-chase off -the-shelf and staying away from more exotic materials used in the defense industry,” says Longtin. “If the industry were to move to requiring a blade produc-ing less radar interference, we think we have some technology that we can draw upon that could help.”
As it matures, the wind energy indus-try faces a number of signifi cant challenges that require collaboration and new, cost-eff ective technologies. As it stands, even
Read this article online | http://short.compositesworld.com/UZFPOTtz.
Read more about the Haliade turbine and other large-rotor installations in “Fair winds for offshore wind farms” | CT June 2013 (p. 32) | http://short.compositesworld.com/fEQbAlC2.
compositesworld.com
without subsidies, wind energy is competitive, or nearly competi-tive, with traditional energy sources, including coal and oil. On-going materials and manufacturing innovation will help push this important end market to wider, and permanent, acceptance. | CT |
Contributing WriterMichael R. LeGault is a freelance writer located in Ann Arbor, Mich., and the for-mer editor of Canadian Plastics magazine (Toronto, Ontario, Canada). [email protected]
akers of amusement park equipment and composites manufacturers have had a long association, the beginnings of which go back at least 50 years to the days when fi ber-
glass began to replace metal and wood in cars and seating for thrill rides, as well as park benches, decorative accessories and other park features. Based on one-off and limited-run parts, amusement park jobs have high per-part tooling costs. But on a water slide project recently completed by SplashTacular (La Quinta, Calif.), Cape Coral, Fla.-based tooling supplier JRL Ventures demonstrated that
tooling costs can be greatly reduced by producing parts of multiple sizes from a resizable mold and a single, reusable vacuum bag.
Built according to design parameters specifi ed in ASTM F2376-08, “Standard Practices for Classifi cation, Design, Manufacturing and Operation of Water Slide Systems,” SplashTacular’s 360Rush slide consists of a 58-ft /17.7m high tower and two curved, enclosed tubes or fl umes, approximately 120 ft /36.6m in length, that feed into a “bowl” at the bottom. Two riders enter the slide through trap doors, descend at speeds up to 40 mph/64 kmh, and then emerge into the
bowl where they spin around its walls before they splash into about 8 inches/203 mm of water at the bottom. Th e ground-level footprint of the slide is approximately 80 ft by 80 ft (24.4m by 24.4m).
SplashTacular had developed the 360Rush design and received a contract to build the slide before a fi re destroyed its facility in Garnett, Kan., where the company’s fi berglass water slide com-ponents had been produced. SplashTacular had already contracted with JRL to build the molds for the slide. Facing a tight deadline, SplashTacu-lar hired JRL to make the parts, too, rather than going through the time and expense of shipping tooling to a third-party fi berglass manufacturer. Not unfamiliar with part production, JRL off ers prototype and fi rst-article production as part of its package of standard toolmaking services.
SplashTacular’s 360Rush,
installed at the Spring Valley
Beach amusement park at
Blountsville, Ala. Its tower and
two enclosed composite fl umes
feed riders into a “bowl” at the
bottom, where they spin around
the rim of the bowl (lower
right) before splashing
into about 20 inches of
standing water at
the bottom.
MINIMAL TOOLS
Water slide manufacturer’s disastrous fi re loss opens door to a closed molding process
that reduces the number — and cost — of production molds, promising future gain.
Maximum thrills
Source (both photos) | SplashTacular
M
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36
TOOLING VENTURE
JRL is a subsidiary of Cape Coral-based Marine Concepts. Engi-neering director Kevin Long says the company has been seeking to grow its share of business in the amusement park market over the past fi ve years. Aft er attending shows, such as the International Association of Amusement Parks and Attractions (IAAPA) in Orlando, Fla., Long says the company realized it couldn’t compete in molds for small, intri-cate parts made primarily in Asia. It did, however, perceive an oppor-tunity in the water park segment, which usually entails the production of much larger parts. SplashTacular’s 360Rush represented JRL’s fi rst signifi cant multimold contract in this market.
JRL primarily used NX CAD soft ware, supplied by Siemens PLM Soft ware (Plano, Texas), to fi nalize the slide design, surface part sections and fair section mating surfaces and edges. Finite ele-ment analysis (FEA) was performed on CAD models of the com-plete slide as part of the design process. SplashTacular used NAS-TRAN FEA soft ware to conduct and analyze a ride simulation of two people descending through the slide and into the bowl. Th e main program inputs were the heights, weights and proportions of the riders. SplashTacular engineers evaluated the simulation to veri-fy that the linear motion of each rider stayed at or below a threshold speed at specifi c locations on the slide. Rider speed and location within the fl umes were assessed to ensure there is no chance two riders will collide as they enter the bowl. Th e contribution of slide design to any anomalies in rider mechanics during the simulation was assessed by SplashTacular engineers, resulting in further modi-fi cation of the CAD model. Additional NASTRAN simulations and iterations continued until an acceptable design was achieved.
MULTI-SIZE CAPABILITY
Several years before the 360Rush project, SplashTacular and JRL had conferred about the possibility of using a modifi ed closed cavity bag molding (CCBM) process that employed partial molds in slide sections. Partial molds are designed with moveable fl anges or blockers that can be repositioned, enabling the company to make parts of more than one size from a single mold. JRL had experience producing some fi rst-article parts with CCBM, which uses a rigid A-side mold and a silicone or elastomeric bag on the B side, but had not tried it with a partial-mold confi guration.
“One of the problems in the past when we tried to use a closed molding process, such as light RTM, is that we had to build a full mold for every part, which gets expensive,” says Jeremy Wilson, se-nior project engineer at SplashTacular. “We just felt there had to be a way to make this happen.”
Wilson credits JRL with make partial molds compatible with the CCBM process by developing a way to use a single reusable bag with a partial mold to produce parts with diff erent lengths. One of the partial molds, for example, makes slide fl ume sections that are 90, 42, and 37.5 inches (2,286, 1,067 and 953 mm) long. Th e length of the bag is dictated by the longest part. Th e blocker is moved to shorten the part length. Th e challenge, then, was to get the bag to seal and hold a vacuum around the blocker and conform to the blocker’s shape. “We had to experiment,” says Kevin Long, project manager at JRL, who reports that they “found a way to make the blocker without any sharp angles or bends so when you pull a vac-
uum and begin to infuse that section, the bag pulls down and seals without infl icting damage.” Th e rubber seal around the fl ange of the entire bag holds the vacuum in that section, and the inherent elas-ticity of the silicone conforms to the shape of the blocker.
Ultimately, the experiment yielded signifi cant savings in tooling cost. Th e slide’s 134 parts were produced with 12 full molds and three partial molds. Notably, the three partial molds, which formed sections of the slide’s fl umes, accounted for more than half of the total parts.
Aft er the fi nal design was approved and the partners were satis-fi ed that their new tooling strategy was viable, tool build was initi-ated with the manufacture of plugs. CAD data was imported into a 5-axis CNC machine for cutting plug components, the majority of which were rough cut, with an undercut shape, out of low-density expanded polystyrene supplied by Carpenter Co. (Richmond, Va.). Th e plugs were sealed with a proprietary resin and coated with ITW SprayCore’s (Clearwater, Fla.) SprayCore 4500, a sprayable, syntac-tic vinyl ester. Th e cured syntactic off ers a hardened layer of material that, Long says, exhibits low shrinkage and is easy to machine. Aft er the plugs were milled, their surfaces were dry- and wet-sanded to a 400-grit fi nish.
Silicone bags for the project were made directly off the tool, rather than
from wax inserts or a hand-layed model. The technique worked well with
slide molds because the parts have large and open shapes and are made
with identical ply schedules.
Fiberglass toolmaker JRL Ventures (Cape Coral, Fla.) developed a method
of using a single reusable bag with a partial mold (below) to produce
parts of different lengths by means of a moveable fl ange or blocker
(colored black). This partial mold can produce slide fl ume sections that
are 90 inches, 42 inches and 37.5 inches in length.
FF
oo
pp
((
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SS
ff
ss
ww Source | SplashTacular
Source | SplashTacular
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Aft er polishing, each plug cavity was prepped with mold release and then coated with Polycryl Corp.’s (Oakland, Tenn.) Diamond-back Y-501 orange gel coat. Next, a layer of 1.5-oz glass mat, sup-plied by Composites One (Arlington Heights, Ill.), was hand layed over the cured gel coat and wet-rolled with Polycryl’s Earthguard EG2500 vinyl ester tooling resin. Two additional layers of 1.5-oz mat were laid and wet rolled over a two- to three-day period. Final-ly, a layer of Earthguard EG3000 high-temperature vinyl ester resin, averaging 0.5-inch/12.7-mm thick, was applied over the glass mat and allowed to cure at ambient temperature to yield molds ranging in thickness from 0.375 inch to 0.75 inch (9.5 mm to 19 mm). Th e cured, demolded tool surfaces were wet sanded to a 600-grit fi n-ish and then power buff ed using a three-step compounding process. Th e blockers for the partial tools were formed by hand laying six consecutive layers of 1.5-oz glass mat, each of which was wet rolled with Earthguard EG2500. Aft er the fi nished tools were supported with steel framing, they were production ready.
One of the unique aspects of manufacturing the slide was the high percentage of split or captive-shape tools. Of the 15 tools produced, 11 were split, including the three partial tools. “Because of the nega-tive draft angles and undercut on many of the slide sections,” Long explains, “you couldn’t remove the part without removing part of the mold.” Th e split molds, therefore, typically feature three or four sec-tions contained or cradled in the tool’s steel-reinforced frame. Rubber gaskets along the seams of the split sections ensure that the molds
hold a vacuum during infusion. An added challenge to the tool de-sign-and-build phase of the project — for partial, split and standard molds — was the complex three-axis part curvature along the length of most slide sections. Th is complicated the tool design and build, as well as part connectivity. “Th e bolt line is not simply a vertical fl ange,” Long points out, “so we had to take care during CAD modeling to ensure all the parts mated 90° to the mating surface.”
MULTI-USE CAPABILITY
For the vacuum bags, SplashTacular and JRL used sprayable grades of silicone supplied by a number of companies. Approximately 0.125 inch/3.18 mm thick, the silicone bags are more expensive than traditional disposable bag materials, but their upfront cost is miti-gated by the fact that they are reusable. JRL further reduced the per-part bag cost on the 360Rush project by pulling the bags directly off the tools, rather than from wax inserts or a hand-layed model. Although this technique is not always advisable, it worked well with the slide molds because the parts have large and open shapes and are made with an identical ply schedule. “In a structure with cores you would not want to build the bag off the mold because you’d create wrinkles,” he warns.
SplashTacular uses in-house resin blending equipment to pro-duce its own gel coats in 180 colors. But because of the blaze, blue and green gel coats (for the inner and outer surfaces of the slide and bowl, respectively) were custom mixed to SplashTacular’s speci-
2 Technicians initiate part production by pulling
a vacuum of 23 to 28 psi on the bag.
3 The mold is infused with an ISO dicyclo-
pentadiene resin that contains a blended
catalyst. The resin enters through two ports
at the top of the bag.
1 After application of the gel coat, a single layer
of 18-oz woven roving is layed up on the mold
and the silicone bag is positioned and secured
over the cavity and fl ange.
5 Once the mold is fi lled, injection lines are
clamped to maintain the vacuum and the
curing process begins. The cured part is
allowed to cool on the mold.
6 The part is pulled from the mold, and its
backside is ready for gel coat.
4 Filling the mold usually takes 12 to 15
minutes, depending on the size of the part.
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INSIDE MANUFACTURING
fi cations by Ashland Performance Materials (Dublin, Ohio) and shipped direct to JRL.
Aft er the gel coat application, a single layer of 18-oz, 0.25-inch/6.35-mm thick woven glass roving was layed up, and the bag was positioned over the cavity and fl ange. A fi berglass ring was clamped to the bag fl ange, and a vacuum of 23 to 28 psi (1.59 to 1.93 bar) was drawn. Th e layup was infused with an ISO dicyclopento-diene (DCPD) resin with a blended catalyst supplied by No. Kansas City, Mo.-based CCP Composites. Th e mold fi ll times varied by part size but generally fell in the range of 12 to 15 minutes.
“Mold fi lling for a specifi c part with CCBM is metered by pump strokes quite accurately,” says Wilson, noting that some of the larg-
er parts require up to 100 strokes to fi ll. Th e largest part, a section of the bowl, was approximately 115 ft 2/10.7m2, and the smallest was about 24 ft 2/2.2m2. Cure, at 108°F/42°C, was complete in about one hour, compared to eight hours for a typical open-mold manufac-turing method. Th e parts, on average, were about 0.25-inch/6.4-mm thick.
“One of the benefi ts of CCBM compared to open molding is a lot less post-mold fi nishing,” Wilson says, reporting that the slide parts required minimal trimming in the fl ange areas and only touch-up sanding at the injection ports. Th e fi nal step in the process was hand spraying the B side with the gel coat used on the A side.
SplashTacular was keen to tap the benefi ts of JRL’s CCBM pro-cess but did not want to sacrifi ce surface quality on the fl ume’s B side, which is vis-ible to park visitors. (In the bowl, the A side is visible.) Ultimately, Wilson says, his team was pleased with the B side, report-ing that the parts had “some typical orange peel” but no fi ber print through. Long says JRL conducted preproduction trial-and-error runs with diff erent fabrics to obtain the smoothest possible B-side fi nish in production.
MULTI-PROJECT CAPABILITY
Th e tooling was fi nished in May 2011, and JRL molded the 134 parts for the slide over a four-week period. Th e 360Rush was operational at Spring Valley Beach amuse-ment park in Blountsville, Ala., in time for the July 4 weekend.
Since then, SplashTacular has moved its manufacturing to a new site and molded two slides for Hawaiian Falls, Th e Colony, near Dallas, Texas, with the same molds and bags used for the 360Rush. And JRL is seeking to solidify its market position by developing a closed-mold process that will provide a better B-side fi nish. | CT |
Read this article online | http://short.compositesworld.com/vqH7gkns.
compositesworld.com
Contributing WriterMichael R. LeGault is a freelance writer located in Ann Arbor, Mich., and the former
editor of Canadian Plastics magazine (Toronto, Ontario, Canada). [email protected]
Contact AOC today at
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PERFORMANCE
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Applications
Applications
Th e city of Austin, Texas, undertook a complex wastewater project that included a new 3.9-mile/6.3-km wastewater tunnel. Because the project was designed to increase wastewater capacity in the down-town district and facilitate residential and business growth in the area, city offi cials knew that it would be important to control odor in and around the tunnel. ECS Environmental Solutions (Belton, Texas) was contracted to provide odor control equipment and relied on Vipel vinyl ester resin from AOC Resins (Collierville, Tenn.) for more than 1,000 ft /305m of fi berglass ductwork and accessories.
Th e ductwork would range in diameter from 12 to 72 inches (305 to 1,829 mm). Approximately half of it would be buried below grade and would have to withstand thousands of pounds of high-density loads from vehicle traffi c. Additional project elements would in-clude fi eld joint kits, fl exible connectors, control and back-draft dampers, bolt gaskets and two 40,000 cfm fi berglass exhaust fans.
ECS manufactured the ductwork using a state-of-the-art comput-erized fi lament winder. Th e fi ber was impregnated with AOC’s Vipel K022 corrosion-resistant vinyl ester resin. “Th e K022 resin was the best choice for this project,” says ECS president Jeff Jones. “Some of the gases in the air stream are corrosive — including hydrogen sulfi de and ammonia. Th ere’s also sulfuric acid. Pipes built with this resin are very resistant to what goes in them and they won’t easily corrode.”
To ease installation, ECS prefabricated and assembled duct sub-sections at its facility before shipping them and a fi eld crew of fi ve
SEWER SYSTEM Corrosion protection for buried odor-control ductwork
to handle fi eld layup, to the construction site in Austin. “We work in a controlled environment in the shop, but in the fi eld you are open to the elements,” adds Jones. “Some of the days we were in Austin were cold and others were really hot. We had to adjust promotion levels and add inhibitors to work with the resin long enough to do a quality job under tough conditions.”
A key factor in the project’s success was that AOC’s Scott Lane, product leader, and Eric Stuck, sales representative, off ered techni-cal assistance as ECS reformulated the resin to meet changing con-ditions in the fi eld. Jones adds, “With the long runs and thick pipes, we went through material much faster than normal, and AOC was very good at meeting this fl uctuation in demand.”
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AOC
Ductile cast iron (cast iron with added magnesium) has been used for manhole covers and frames since the mid-20th Century due to its durability and high compressive strength. Engi-neers who design underground infrastructure have rarely considered the use of alternative materials. However, operators of localized multibuilding heating systems, such as those on college campuses, have become increas-ingly aware of the dangers
posed by cast-iron manhole covers. Cast iron becomes very hot when exposed to internal steam and external sunshine, and it also conducts electricity — a concern when manhole covers are located in walkways where students wear sandals or go barefoot in warm weather. In addition, although cast iron stands up to heavy loads and severe impacts, it is very heavy — the density of a cast-iron manhole cover can be as high as 450 lb/ft 3 (7,208 kg/m3). A small 32-inch/813-mm diameter cover can weigh as much as 250 lb/113.4 kg, which can lead to injuries to workers who have to move them.
Th ese factors led the utilities department of a leading engineer-ing university based in Cambridge, Mass., to replace traditional manhole covers with composite versions manufactured by Fibre-lite Composites (Skipton, North Yorkshire, U.K., and Pawcatuck, Conn.). Many other universities in both the U.S. and Canada have since followed suit, says the company.
Fibrelite uses multiaxial and woven glass reinforcements to make a preform with a fi ber architecture that maximizes bending stiff ness and strength-to-weight ratio. Th e preform is then infused with polyester in a resin transfer molding process; for higher-tem-perature or highly corrosive applications, vinyl ester resin is used. Th e thermal gradient properties of Fibrelite’s composite covers sig-nifi cantly reduce heat transfer from the steam vault below — the surface temperature of the cover is typically only slightly higher than the ambient temperature. Extensive testing has shown that composite covers stay cool to the touch and support the same wheel loads as 32-inch cast-iron manhole covers, yet they weigh nearly 70 percent less. Fibrelite emphasizes that its cover eliminates the pos-sibility of electrical shock and resists corrosion caused by salts, oils, water and steam and avoids theft of cast-iron covers, which have value as scrap metal. As an added incentive, Fibrelite can perma-nently mold into the cover’s top surface any style of school logo or other marking in single or multiple colors.
MANHOLE COVERS Composites replace cast iron on university campus
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Calendar
Oct. 2-3, 2013 High-Performance Composites for Aircraft Interiors Seattle, Wash. | www.compositesworld.com/ conferences
Oct. 2-4, 2013 JEC Americas 2013 Boston, Mass. | www.jeccomposites.com/ events/jec-americas-2013
Oct. 3-5, 2013 Turk Kompozit 2013 Istanbul, Turkey | http://turk-kompozit.org/en
Oct. 15-17, 2013 BIOFIBE 2013 Winnipeg, Manitoba, Canada | www.biofi be.com
Oct. 15-17, 2013 MATERIALICA 2013/eCarTec Munich, Germany | www.materialica.com
Oct. 21-24, 2013 SAMPE Tech Conference Wichita, Kan. | www.sample.org/events
Oct. 24-26, 2013 India Composites Show 2013 New Delhi, India | www.indiacompositesshow.com
Oct. 28-29, 2013 The Composite Decking and Railing Conference 2013 Baltimore, Md. | www.deckrailconference.com
Oct. 29-31, 2013 SAMPE China 2013 Shanghai, China | www.sampe.org.cn
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Nov. 6-7, 2013 Chemical Processing Symposium 2013 Galveston, Texas | www.acmanet.org (click ‘events’)
Nov. 12-13, 2013 Composites Engineering Show 2013/ Automotive Engineering Birmingham, U.K. | www.compositesexhibition.com
Nov. 19-21, 2013 EWEA Offshore 2013 Frankfurt, Germany | www.ewea.org/events
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Dec. 9-12, 2013 Carbon Fiber 2013 Knoxville/Oak Ridge, Tenn. | www.compositesworld.com/conferencesD
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2014 Orlando, Fla. | www.nodigshow.com
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New Products
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Compression shuttle pressLMG (De Pere, Wis.) has introduced its largest-ever shuttle press. The 900-ton system has a mold die capacity of 126 by 116 inches (3,200 by 2,946 mm). The total length of the press and shuttle system is 39 ft/11.9m. The platen movement is facilitated by eight main rams and two jack cylinders. Accurate platen parallelism is achieved with 45° adjustable gib guides on four of its rectangular tie rods. The press was built to mold heavy parts as large as 56 ft²/5.2m². Its shuttle system is designed to move the lower
mold half to the outboard station for material loading and to shuttle the just-molded part to the opposite side for unloading. The press has a mold load feature on the shuttle table that incorporates pins that come up through the table to support the mold above the table as it is loaded via forklift truck. After the forklift truck moves away, the pins lower the mold into proper position. The press is controlled with an Allen Bradley PLC. www.lmgpresses.com
Hybrid structural adhesivesADERIS's (Le Thillay, France) fi rst line of hybrid structural adhesives, called INES (INterlaced Elastomer NetworkS), are said to offer high structural and sound-damping performance (suitable for automotive parts). The line reportedly requires no primer on joint members and combines the per-formance of three adhesive bonding technologies: the resistance and mechanical strength of epoxies; the elasticity provided by polyurethanes (PUR); and the fast assembly rate enabled by methyl methacrylates (MMA). ADERIS says this is the fi rst time a structural adhesive combines elongation, low modulus and high mechanical performance with high impact resis-tance and peel and shear strengths — 70 percent pure elasticity over an elongation range in combination with high strength (250 kg/cm2 for shear on steel and up to 100 kg/3.5 cm for peel) — and it does so in a range of temperatures from -80°C to 140°C (-112°F to 284°F). The resulting bond remains fl exible, yet bonded parts may be handled soon after they are joined. www.aderis-specialties.com
HP-RTM for automotive moldingKraussMaffei's (Munich, Germany) new RIM-Star high-pressure resin transfer molding (HP-RTM) production cell is designed for series production of carbon fi ber-reinforced composite components that are paintable direct
from the mold. The system will soon be used to mold roof shells, with a 50 percent fi ber volume, for the Roding Roadster Targa (Roding Automotive GmbH, Roding, Germany). The polyurethane matrix resin will be prepared by two RIM-Star Nano 4/4 metering machines, which are equipped for high-temperature process control with material temperatures up to 80°C/176°F. The wear-optimized machine design reportedly will ensure permanent pro-cess stability with polyamide (PA), polyurethane (PUR) and epoxy resins. The machine’s centerpiece is a new RTM mold carrier with a compact design and a clamping force of 3,800 kN. The mold fi xing area (1,300 by 1,300 mm, or 51.2 by 51.2 inches) is said to be ideal for auto components as large as 1m²/10.8 ft². www.kraussmaffei.com
Pourable, addition-curing siliconeWacker Chemie AG (Munich, Germany) has developed ELASTOSIL
VARIO,
a modular system for pourable silicone rubber compounds with two com-ponents that enter into an addition reaction at room temperature in the presence of a platinum catalyst. The system permits adjustment of the compound's reactivity and the hardness of the cured elastomer, enabling compounders and silicone processors to tailor-make products. Suitable for encapsulating and coating, for making technical molded parts and for mold-making, the system consists of four modules: two base components and two catalyst components. The former can be blended together in any ratio, and so can the latter. From these modules, the processor mixes the two compo-nents of the RTV-2 silicone rubber compound in the quantities needed for curing. The mixing ratios for the base and catalyst components can be varied to match the silicone to the application. The hardness of the cured rubber is determined by the ratio of the two base components in the mixture; Shore A durometers range from 15 to 40. www.wacker.com
Fatigue analysis for wovensSafe Technology Ltd. (Sheffi eld, U.K.) says the latest release of Safe’s fe-safe/Composites (the add-on module to Safe’s fe-safe suite of fatigue analysis software for fi nite element models) features a new tool for fatigue analysis of woven fi bers. Developed by Safe Technology and Firehole Com-posites (Laramie, Wyo., now part of Autodesk Inc., San Rafael, Calif.), the module also extends current capabilities to new microstructures and loading defi nitions, and it supports fatigue life predictions of plain-weave micro-structures, using the same physics-based solution as that already applied to unidirectional composites. Fatigue life predictions now can be completed for multiaxial load states for which the material is not characterized. Further, the applicable loading defi nitions have been expanded to allow for multiple repeats and block loadings — useful for defi ning complex duty cycles (a function used widely by wind turbine blade manufacturers). Finally, the ef-fects of material healing at low stress levels have been included to accom-modate infi nite life scenarios that are often encountered in analyses with low loads applied for long histories. www.safetechnology.com
Marketplace
Marketplace
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Available in various temperature ranges
Fax Website: http//:www.generalsealants.comE-mail: [email protected]
Used world wide by composite manufacturers
Distributed by:AIRTECH INTERNATIONAL INC.
Tel: (714) Website: http//:www.airtechintl.com
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MANUFACTURING EQUIPMENT & SUPPLIES |
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COMPOSITES SOURCES
Workholding Solutions for Metal, Composites, Ceramic and Glass.
800-810-2482 • www.northfield.com
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Showcase
INDEX OF ADVERTISERS
Showcase
Product & LiteratureSHOWCASE
ms
ReleaseAgent
Dry Lubricant
MS-122AD
PERFORMANCE PTFE RELEASE AGENTS/DRY LUBRICANTS FOR COMPOSITES
MILLER-STEPHENSON CHEMICAL COMPANY, INC.
www.miller-stephenson.com 800.992.2424
The Companies of North CoastNorth Coast Tool & Mold Corp.North Coast Composites, Inc.
www.northcoastcomposites.com216.398.8550
A&P Technology Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Airtech International . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
AkzoNobel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ACMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
AOC LLC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Ashby Cross Co. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Baltek Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
CCP Composites US . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Chem-Trend Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Composites One LLC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
DIAB International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Dieff enbacher GmbH. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Elliott Co. of Indianapolis Inc. . . . . . . . . . . . . . . . . . . . . 11
Henkel Corp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Interplastic Corp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
ITW Polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
JRL Ventures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Knoxville Oak Ridge Innovation Valley . . . . . . . . . . . . 21
McClean Anderson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
North Coast Composites . . . . . . . . . . . . . . . . . . . . . . . . . 25
Ross, Charles & Son Co. . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Saertex USA LLC . . . . . . . . . . . . . . . . . . . . . . . Back Cover
SPE Automotive Division . . . . . . . . . . . . . . . . . . . . . . . . 14
Technical Fibre Products Ltd. . . . . . . . . . . . . . . . . . . . . . 33
TenCate Advanced Composites USA . . . . . . . . . . . . . . 10
Tricel Honeycomb Corp. . . . . . . . . . . . . . . . . . . . . . . . . . 42
Wisconsin Oven Corp. . . . . . . . . . . . . Inside Back Cover
Wyoming Test Fixtures Inc. . . . . . . . . . . . . . . . . . . . . . . 15
Zyvax Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inside Cover
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The U.S. Navy wisely opts for more expensive submarine
moorings that maximize lifecycle cost-effi ciency.
his story begins with an unlikely premise: the U.S. Navy needed to solve a problem, and it was willing to spend more money up front on a solution if that solution promised
net savings in the long run. Th e problem? Poor durability of its deep-draft submarine camels. Th ese large and mostly submerged metal or wood structures are attached to a mooring structure and fi tted with rubber bumpers to provide a buff er between the Navy’s submarines and the waterfront where they are berthed. Th e camel defl ects or compresses with vessel movement and prevents damage to the hull, diving planes, screws, fairings, special skin treatments and other equipment by absorbing the sub’s energy — which is considerable, given the 560-ft /171m length and 17,000 tons of water displaced by berthed vessels, including the Ohio class submarine, the heaviest in the fl eet.
Given the saltwater environment in which they work, metal and wood camels require removal every two years for inspection and repair, which can be substantial if corrosion has begun. Th e other challenge the Navy faced was that it had 17 unique camel designs in ports around the world. Each camel was designed to accommodate a specifi c submarine type, which, in addition to the Ohio, includes the Los Angeles, Virginia and Seawolf classes.
WIN WITH LONG-TERM DURABILITY
Composite submarine
camels
Design and engineering fi rm Whitman, Requardt & Assoc. (WR&A, Baltimore, Md.) and composites manufacturer Composite Advantage (CA, Dayton, Ohio) were tasked with developing a uni-versal composite camel that would meet that challenge and accom-modate any U.S. Navy sub type, anywhere in the world.
Th e Navy’s criteria for the new camel included not only the abil-ity to absorb the energy generated by a berthing submarine, but also the freeboard (how much of the camel would sit above the wa-terline), the list and trim angles, and the overall fl otation stability requirements. Th e Navy’s request for proposal (RFP) specifi ed that the level fl oating position of the camel must be maintained within a 1-inch/25.4-mm tolerance side to side and front to back. Further, the freeboard must be maintained within a 1-ft /0.3m tolerance.
Th e RFP also stipulated that the camels must meet performance requirements in three load scenarios: berthing of a submarine, mooring of a submarine and lowering and lift ing the camel into and out of the water. Berthing assumes a submarine velocity of 0.4 ft /sec (0.12m/sec), which is approximately 200 ft -kip of energy. Mooring loads — caused by waves, wind and other forces — are, by compari-son, smaller than berthing forces. Th e load path for berthing and mooring are horizontal, but the load path for lowering and lift ing
the camel into and out of the water is vertical; discrete lift ing points on the camel, therefore, would be required and would have to withstand an anticipat-ed mass in excess of 45 metric tonnes (100,000 lb).
“We were dealing with a unique shape and the criteria were somewhat at odds with each other in that if we designed to meet one requirement, issues surfaced with the other criteria,” says Matthew Lambros, struc-tural engineer for WR&A. “Th is was largely due to the fact that a number of properties aff ecting the camel, such as volumes and
A fi nished camel awaits the berthing of a submarine.
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Illustration | Karl Reque
ENGINEERING CHALLENGE:
Design a composite camel that meets the U.S. Navy’s requirements for energy absorption, stability and long service life and can berth subma-rines of all classes.
DESIGN SOLUTION:
A modular composite sandwich construction that allows camel bal-last to be customized to meet trim and freeboard requirements while absorbing the energy of berthing submarines.
COMPOSITE ADVANTAGE’S UNIVERSAL CAMEL FOR U.S. NAVY SUBMARINE BERTHS
densities, can vary and must be considered to establish precise fl ota-tion calculations.”
Working with CA, WR&A developed a design that comprises fi ve composite structures, or modules, that are assembled on site to build the 25 ft by 9 ft by 11.5 ft (7.6m by 2.7m by 3.5m) camel. CA president Scott Reeve says the two largest modules, the upper and lower main boxes, are stacked (see photos). Two others, called wing walls, are installed on each side of the stack, and a third module is front mounted to provide the surface that faces the submarine. At-tached to this front surface are the rubber fenders that contact the submarine. On the backside of the camel, a series of ultrahigh mo- lecular weight polyethylene rubbing strips provide a contact surface where the camel meets the fi xed dock structure.
Th e modules are made by assembling and bonding compos-ite panels. Most panels have a sandwich construction, featuring 3.5-inch/89-mm thick TYCOR foam core (Milliken & Co., Spar-tanburg, S.C.) faced and edged with 0.3-inch/7.62-mm thick lay-ers of uniaxial and triaxial glass fi ber fabric from V2 Composites
(Auburn, Ala.). Th is structure is hand layed, vacuum bagged and infused with Hetron 992 or Derakane 610 vinyl ester resin, supplied by Ashland Performance Materials (Dublin, Ohio). Th e foam core incorporates fi berglass shear webs, spaced at 1.5 inch/38.1 mm in-tervals. Where the panels are subjected to biaxial bending or sig-nifi cant shear forces, a bidirectional core is used. Th is consists of unidirectional core that is cut into short lengths (perpendicular to the shear webs) and wrapped in additional fi berglass fabric, thus providing shear webs in both directions.
Reeve says some of the camel’s primary contact points — those that see the most physical and mechanical stress — are designed for impact resistance as 1.5-inch/38.1-mm thick solid laminates. Each module and, later, the entire camel structure, is bonded together with an adhesive provided by SCIGRIP (Durham, N.C.).
Structural analysis of the camel included a 3-D fi nite element analysis (FEA) of the entire structure, using RISA-3D FEA model-ing soft ware developed by RISA Technologies (Foothill Ranch, Ca-lif.). Th e model consisted primarily of a series of meshed plate
• Must withstand lifting mass in excess of 45 metric tonnes (100,000 lb)
• Must withstand berthing submarine velocity of 0.4 ft/sec (0.12m/sec) or ~200 ft-kip of energy
EXPLODED VIEW
FRONT VIEW
TOP VIEW
Rubber fenders
Wing wall
Wing wall
11.5 ft/3.5m
9 ft/2.7m
Rope ties
Deck
Upper box
Wing wall
Lower box
Front module
Front module w/ fenders
25 ft/76m
Wing wall
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Read this article online | http://short.compositesworld.com/fU1KgKnR
elements; the material and section properties of the plate elements were input manually to match the properties of the composite sand-wich panels. Berthing, mooring and lift ing (gravity) loads were ap-plied to the model, and the resulting forces were used for panel and connection design. Th e submarine berthing energy absorbed by the marine fenders was converted to a force using charts and tables pro-vided by marine fender manufacturers. Th e contact points from the camel to the mooring structure were modeled using compression-only lateral supports.
Th e panel properties were determined through an extensive test-ing program developed specifi cally for the camel design. For each failure mechanism identifi ed in the structural analysis, the panel properties from the testing program were compared to the results of the analysis to determine the factor of safety against failure. Reeve says the calculated factors of safety were discussed with the owner, engineer and fabricator to ensure there was a consensus regarding their acceptability. Where possible, the safety factors also were com-pared to industry standards. For safety factors that were determined to be insuffi cient, changes to the design or fabrication methods were made as required.
FABRICATING FOR FLOTATION
Aft er the camel’s design was fi nalized and manufacturing began, Reeve says another challenge presented itself: buoyancy manage-ment. Almost all of a camel rests below waterline, but the composite camels are inherently too buoyant for the application. Th e goal, then, was to put the camel’s center of gravity as far as possible below the waterline to maintain rotational stability — easier said than done.
Reeve says calculating the center of buoyancy and center of gravity included the tedious process of determining the relative po-sition and density of each camel component, including panels, fl o-tation foam, marine fenders and connection angles and hardware. Increasing the ballast weight to achieve the required freeboard, for example, would impact the angle of fl otation. Th e fi nal solution had to achieve a balance among all the design criteria.
Ultimately, says Reeve, CA determined that ballast must be add-ed to submerge the camel and keep it trim against the submarine.
Th is is done in three ways. First, aft er the 70,000-lb/31,751-kg camel is assembled, 35,000 lb/15,876 kg of concrete is poured into the cen-ter box. Second, a series of movable steel plates are installed over the ballast; they are adjusted from side to side in the box aft er the camel is fl oated for the fi rst time to bring the entire structure trim. Th ird, holes are drilled in the box sides to allow them to fi ll with water. “Th e water helps keep the structure stabilized,” says Reeve. “It doesn’t bob or move as much.”
CA’s fi rst camel was assembled on site at Naval Submarine Base New London (Groton, Conn.) in October 2010 and installed a month later for a fl otation test. Since then, the Navy has installed two more camels, and CA is now manufacturing another for Naval Station Norfolk (Norfolk, Va.). “Feedback from Navy facilities engi-neers and port operations is very favorable,” says CA vice president Andy Loff . “Elimination of recurring maintenance is a major opera-tional benefi t, and multiple bases are now looking at the composite camels for future use.”
Reeve says the Navy is installing about two composite camels per year and is looking at other camel-like applications for the material, despite the fact that the CA camels cost 40 to 50 percent more than the old metal and wood versions. He lauds the unusual foresight: “Th e Navy basically said, ‘I’d much rather pay a little more up front than pay a lot more over a 10-year period.’” And with camels now expected to last 25 years or longer, the savings will live on. Mission accomplished. | CT |
Editor-in-ChiefJeff Sloan, CT’s editor-in-chief, has been engaged in plastics- and composites-industry journalism for 20 years.jeff @compositesworld.com
The camel’s upper and lower boxes, each
about 9.1 ft tall by 25 ft wide by 11.5 ft deep
(2.8m by 7.6m by 3.5m), are stacked prior to
the addition of the wing walls, each 17.8 ft tall
by 5.5 ft wide by 11 ft deep (5.4m by 1.7m by
3.4m), visible at left and foreground.
With center boxes and wing walls assembled,
the fi fth box, the front fender — measuring 18-ft
tall by 12-ft wide by 3.5-ft deep (5.5m by 3.7m
by 1.1m) — will be attached to the shadowed
area on the front of the center boxes.
An assembled submarine berth camel is
lowered into the water.
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