NASA-CR-19860 !

Department of Civil Engineering

College of Engineering and Technology

Old Dominion University

Norfolk, VA 23529

,af

POLYMER INFILTRATION STUDIES

By

Joseph M. Marchello, Principal Investigator

Final ReportFor the period October 1, 1993 - April 30, 1995

Prepcred for

National Aeronautics and Space Administration

LanOey Rcsrmch CenterHampton, V'uginia 23665

UnderNAG-l-1067

Norman J. Johnston, Technical Monitor

MD-Polymefic Materials Branch

Submitted by theOld Dominion Umiversity Research Foundation

P.O. Box 6369

Norfolk, Vhlbb 23508-0369

May 1995

i_,

m m

N III

fJ 4'O_ C 0Z _ 0

N

https://ntrs.nasa.gov/search.jsp?R=19950021436 2020-06-03T16:26:13+00:00Z

bKs

Final Report

POLYMER INFILTRATION STUDIES

Summary

Significant progress was been made during the

project on the preparation of carbon fiber composites

using advanced polymer resins. The results were set forth

in quarterly and annual reports and in publications and

presentations at national and international meetings.

Among the research activities and achievements

reported therein are:

- Assistance in acquisition of bench scale automated

prepreg placement, ATP, equipment at NASA-LARC

- Participation in the design and operation of a

Prepregger for solution and hot sled operation in

making tape from polymer solutions and from powdercoated tow

- Ribbonizing Powder-Impregnated Towpreg

- Experimentally determine short -time ribbonbonding kinetics for In-situ ATP.

- Powder Curtain Prepreg Process development.

- Textile applications of powder coated tow.

Polymer Infiltration Studies

Polymer infiltration investigations were directed

toward development of methods by which to produce

advanced composite material for automated partfabrication utilizing textile and robotic technology in

the manufacture of subsonic and supersonic aircraft. This

object was pursued through research investigations at

NASA Langley Research Center and by stimulating

technology transfer between contract researchers and the

aircraft industry.

Proiect Results

The findings and results of the project are

summarized in the following paper entitled " Powdered-

Coated Towpreg: Avenues to Near Net Shape Fabrication of

High performance Composite". This paper will be presented

at the ICCM-10 Conference in Vancouver in August 1995.

Twenty-nine papers were written during the course of

the grant. The are presented in the following list of

publications. Copies of these papers were included in the

appropriate quarterly and annual reports, and are

available on request.

Two patents were issued during the grant and four

additional patent applications have been submitted.

Copies of the first patent was submitted earlier. A copy

of the second one is attached. Copies of the patent

applications were included in quarterly reports and are

available on request.

•/

POWDER-COATED TOWPREG: AVENUES TO NEARNET SHAPE FABRICATION OF HIGH PERFORMANCE

COMPOSITES

N. J. Johnston and R. J. Cano

NASA Langley Research Center

J. M. Marchello

Old Dominion Universityand

D. A. SanduskyThe College of William and Mary

ABSTRACT

Near net shape parts were fabricated from powder-coated preforms. Key issues including

powd_-r, loss during weaving and tow/tow friction during braiding were addressed, respectively,by fumng the powder to the fiber prior to weaving and applying a water-based gel to the towpregprior to braiding. A 4:1 debuiking of a cotoplex 3-D woven powder-coated preform was

achieved in a single step utilizing expansion rub.ber, molding. Also, a proce.u, was devel.oped fo rusing powder-coated to.wpreg to fabricate.consolkl, ated rib.bo.n having good dtmenstonal mtegrttyand low voids. Such nbbon will be reqmred for m situ fabrication of structural con_..port,ents _aheated head advanced tow placement. To implement process control and ensure high quahtyribbon, the fibbonizer heat transfer and pulling force were modeled from fundamental principles.Most of the new ribbons were fabricated frown dry polyarylene ether and polyimide powders.

INTRODUCTION

In the last several years, powder impregnation of carbon fibers has. been .gr.eatly refined atLangley Research Center to I_'ovide a low cost mrtmg material for fabricating high performancecomposites from high melt viscosity difficult-to-process matrix materials [ I ].

Two paths are being pursued in composite part fabrication from powder-coated towpreg. The

towpreg is being woven and braided into various textile preforms which are thermoformconsolidated into a final part. Alternately, towpreg is being converted into a thin consolidatedribbon for lay-down in heated head automated tow placement machines.

TEXTILE APPLICATIONS

Compression or autoclave molding of textile preforms made from polymer powder-coated yarnsoffers an alternative to resin transfer molding for the fabrication of net-shape parts. Powder

coating the fiber bundle prior to weaving or braiding requires special consideration for both

textileprocessingandfor thesubsequentdebulkingof thepreforms[21. Carbonfiber (6K and12K AS4, Hercules) coated wtth epoxy thermoset powder (AMD0036, 3M Company) was usedin the textile studies.

Methods of treating the powder-coated towpreg to improve its "braidability" included towpreg

twisting, serving with a polyvinyl alcohol (PVA) monofila .ment, remelting the powder duringbraiding and application of surface lubricants such as zinc stearate, hydroxyl-terminatedpolyethylene glycol (PEG) and polyacrylic acid.

Powder-coated towpreg was twisted 15 twists per meter, a standard level for carbon fibermanufacturers. Earlier studies showed that this twist level had no significant effect on themechanical properties of woven and unidirectional composites. However, braiding efforts wereunsuccessful because twisting did not sufficiently decrease the surface friction of the towpreg.

Serving the powder-coated towpreg with polyvinyl alcohol (PVA) monofilaments in a double

helix wrap .l_..uced a yarn that was round and tightly compacted. The tightly served yarnsbraided much like wires or monofilaments - a condition that was not conducive to achievinggood lay-down and full coverage of the mandrel.

Surface glazing, by re-melting the powder on the surface of the towpreg during the braidingoperation was reed. While the glazing treatment reduced, friction, the adhesive properties of theresin caused the tows to stick together and preclude successful braiding.

Application to the towpreg of. a. small amount (5 percent) of zinc stearate powder wasinvestigated as a means of achtevmg dry lubrication. In particular, the need for lubrication oftowpreg yarns was most apparent when axial yarns are required in the final fabric. Thistreatment was successful anda tight braid of 10 ends per inch with a 6K towpreg was achieved.

The subsequent fabric was processed into composite panels which, unfortunately, were voidy andyielded poor mechanical properties.

One of the major reasons PEG was selected as a lubricant is the fact that it is soluble in andreacts with epoxies. Towpreg, surface coated with it at a level of I-2 percent, exhibited no

significant increase in lubricity, lloweve.r., at .aconcentration of 10 percent, the yarn's lubricatingquality was significantly increased. Unidtrecttonal composites were made of towpreg coated at 2and I0 percent levels to evaluate the effect on mechanical properties. Composites made fromtowpreg containing 10 percent PEG consolidated badly. Their void contents were above 5percent. The material coated with 2 percent PEG consolidated well and exhibited goodinterlaminar shear and flexural properties even at elevated temperature.

Surface application of less than I percent polyacrylic acid gel provided towpreg with reducedfriction. Successful braiding on standard equipment was achieved by first rewinding the gel,coated towpreg onto braiding spools or cops. Since the gel is 99 percent water, most of the waterevaporated and the towpreg was dry by the time the braider was loaded with bobbins and theprocess started. Water was sprayed onto the towpreg yarns once they reached the cross-overregion. The lubricating properties of the gel were reactivated with the spray water and a highquality triaxialy [00/#60 °] braided fabric with 10-11 ends per inch was obtained using 6K

towpreg. The interlaminar shear and flexural properties of composites made with this productwere identical to those obtained from control specimens made with untreated towpreg, even at

elevated temperatures [3]. While both the PEG .a.nd the polyacrylic acid gel enhancedbraidability, the latter was preferred because of its ability to be reconstituted wtth water and thelow concentrations required for achieving high lubricity.

With powder-coated textile preforms, a higher resin content is necessary in order to fill allinterstitial spaces. However, consideration must be made for the greater amount of debulking

that occu_ dt_ng consolidation. Consolidationof powder-coated textile structures requires a

cure process which will accommodate an approximately 4 to l change in thickness of the bulkywoven or braided preforms. Previously, '-mghj_rocesses were used to fabricate bladestiffened structures made from powder-coated oecausetowpreg of the large amount of debulkingthat is required.

Recently, the ability of high temperature cast silicone rubber tooling to expand and p..md,ucesignificant pressu.re at the cure temperature has been demonstrated [4]. A modified sthconerubber system destgned to produce accuratelratepressure application at predetermined temperature

levels was combined with movable hard tooling to develop a _ debulking and cure processto fabricate composite structure from textile preforms. Upon visual and mtcroscoptcexamination, an integrally woven blade stiffened was found to be well-consolidated, wrinkle-freeand to have I percent voids (Figures I and 2).

TOW PLACEMENT RIBBON

Automated tow placement (ATP) is one of the most important new techniques for rapid, costeffective, net shape composite fabrication. The technique has 2 approaches. In one, tacky

drapeable thermoset tape is robotically applied to a tool followed by autoclaveconsolidation/cure. In the other, which the Langley Research Center ts emphasizing, apreconsolidated thermoplastic ribbon is thermo-welded on-the-fly. The latter provides in-situconsolidation and obviates the need for autoclave Wocessing, thereby reducing costs. Manycommercial research efforts are developing the heated head robotic hardware and associatedsoftware to bring this technology into widespread use in building aircraft parts.

As these ATP developmental research efforts succeed and fail, important limitations and "bottle-

neck" issues have been discovered. Examples include open section residual str¢. sacs, turningradius limitations, autohesion reqmrements, compliant roller issues, prepreg matenai quality andpost process annealing of crystalline polymers. Most basic of these is the requirement for highquality, fully consolidated, narrow width thenrJoplastic prepreg ribbon.

Dry powder prepregging of thermoplastics is efficient in distributing solid polymer particlesthroughout continuous filament tows. The resulting towpreg yarn is flexible, bulky and abrasive.Robotic placement material handling systems are generally designed to utilize stiff,preconsolidated ribbons with consistent cross-section. Research was initiated to develop abench-scale processing method to convert I or 2 powder-coated towpreg yarns into a fullypreconsolidated narrow width ribbon acceptable for ATP studies [5}. A comprehensive study ofdebulking techniques revealed a variety of issues critical to effective ribbonizing includingtowpreg material quality, transverse squeeze flow, appropriate timing for heating and pressureapplication and tool contact/release.

Several processing techniques were designed, built and experimentally evaluated to serve as abasis for understanding the unique characteristics of the towpreg ribbonizing process. Use ofreactive plasticizers or solvents was excluded from this study. Three powder towpreg yarnmaterials, Aurumm-500/IM-8 (prepregged by CYTEC), LARCm-IA/IM-7 and PEEK/AS-4

PereP,ragged .by NASA LaRC), were used in the evaluation of these processes. By utilizingsiravse attrioutes of several of the experimental processes, a novel processing technique was

developed (Figure 3). The work concentrated on the fabrication of a 0.63 cm wide ribbon fromtwo 12K ]M-7 powder-coated tows.

This powder coated towpreg ribbonizer was comprised of two primary components. The hot barfixture facilitated transverse melt squeeze flow while the cool nip-roller assembly solidified theribbon into a preconsolidated ribbon with consistent cross-section. The heat transfer and pullingforce were modeled from fundamental principles to develop a basic understanding of the process

and help adaRt it to a variety of polynleri_ materials and cure situations. The process hasprovided quality ribbon from a variety of other hlgh-temperature thermoplastic powder-coatedtowpreg yarns. The observed experimental rates and temperature ranges indicate that thistechnique could be readily integrated as a final step in the powder prepreg manufacturingprocess.

CONCLUDING REMARKS

Significant vrogress has been made in preparing near net shape pans from powder-coated

pref..o_ms. The key issues ad .d.ressed include powder loss during weaving, tow/tow friction duringbratding and preform debulkmg. To reduce losses, the powder was fused to the fiber prior to

weaving. Braiding difficulties were overcome by applying a water-based gel to the towpreg. A4:1 debulkmg of a complex 3-D through-the-thickness woven blade-stiffened preform wasachieved in one experiment in 2 steps; in another, a single step method utilizing expansionrubber molding was used.

A process was developed for the fabrication of ribbon having good dimensional integrity and lowvoids and useful for heated head ATP studies. In order to implement process control and ensure

high quality ribbon, the heat transfer and pulling force were modeled from fundamentalpnnciples. These new ribbons, fabricated mostly from dry polyarylene ether and. polyimidepowders, are currently undergoing in-situ lay-down and evaluation. Quality ribbon ts critical tothe future development of the hardware for this new technology.

REFERENCES

I. R. M. Baucom and J. M. Marchello, Powder Curtain Prepreg Process. J. Adv. Mater. 25,31-36 (1994).

.

3

M. K. Hugh, J. M. Marchello, R. M. Baucom and N. J. Johnston, Textile Composites fromPowder Coated Towpreg: Weaving Protocol. Sci. Adv. Mad. Process Eng. Series. 36,1045-1050 (1992).

M. K. Hugh, J. M. Marchello, J. Y. tlartness, S. Goodwin, J. G. Shields and N. J. Johnston,Textile Composites from Powder-Coated Towpreg: Yarn Treatment for Braiding. Sci. Adv.Mad. Process Eng. Series. 39, 551-559 (1994).

o E. S. Weiser, J. M. Marchello, M. K. Hugh, R. M. Baucom and J. J. Snoha, One-StepConsolidation of Powder-Coated Composite Preforms. lnternatl. SAMPE Tech. Conf.Series. 26, 462473 (1994).

. D. A. Sandusky, J. M. Marchello and N. J. Johnston, Ribbonizing Powder ImpregnatedTowpreg. Sci. Adv. Mad. Process Eng. Series. 39, 2612-2625 (1994).

v

Figure" I, Pht_t(_gr:tl_h of the a._,-fal_ricat_'d,rul_l_'r cxpan._icm mohled l_httle .qtiffenerwith f'la,_hing tm Otll('r eclges.

Figure 2. Pht)tograph of the fi111ycon._olidated I_la(le stiffener fnbricnted by the onestep process aftt-r tn:tc'hJning ha,s been perft_rmed.

,_,__

t iil,l_ z

j " ||_

ill

J

i , l

7

• o

Publications

"Recent Developments in Dry Powder Prepregging on Carbon Fiber Tows," J.L Throne, R.M.Baucom, and J.M. Marchello, FiberTex Conference Transactions, Clamson University, October1989.

"I_aRC Powder Prepreg System," Robed M. Baucom and Joseph M. Marchello, 35th InternationalSAMPLE Sedes, 3...55(1), p. 175-188, Apd11990.

"I.aRC Dry Powder Towpreg Systems," Robed M. Baucom and Joseph M. Mamhello, NASATechnical Memorandum No. 102648, 49p, April 1990:

•Powder Towpreg Process Development," R.M. Baucom and J. M. Msmhello, Transactions of theFirst NASA Advanced Composites Technology Conference, p. 443-455, Nov. 1990.

"Study of Flexuml Rigidity of Wearable Power-Costed Towpreg," Douglas E. Hirst, Joseph M.Mamhello, and Robed M. Baucorn, Transaction of the 22nd International SAMPE Technical

Conference Transactions, p. 360-369, November 1990.

"Composites from Powder-Costed Thermoplastic and Thermoset Prepreg," Joseph M. Mamhelioand Robert M. Baucom, Eight Thermoplastic Matrix Composites Review, San Dlego, CA 8 p.8-15, January 1991.

"I_aRC Powder Towpreg Process," Joseph M. Mamhelio and Robert M. Baucom, Transactions36th International SAMPE Symposium, pp. 68-80, Apdl 1991

"Powder Towpreg Process Development," Robert M. Baucom and Joseph M. Mamhello,Transaction of the First NASA Advanced Composites Technology Conference, P. 443-455,Nov 1990.

"Weaving Towpreg Made from Dry Powder Prepregging," Maylene K. Hugh, Joseph M.Marchello, Janice Maiden, and Norman J. Johnston, Fiber-Tax Conference, North CarolinaState University, October 1991.

,Composites from Powder Coated Towpreg: Studles with Variable Tow Sizes," M.K. Hugh, J.M.Mamhello, R.M. Baucom and N.J. Johnston, Transactions of the 37th Intematlonal SAMPESymposium, March 1992. ..

"Wesvability of Dry Powder Towprsg," M.K. Hugh, J.M. Marchello, J. Madan and M.J. Johnston,Proceeding, Third Advanced Composites Technology Conference, NASA-ACT Program, LongBeech, CA, June 1992.

"Customized ATP Towpreg," D.A. Sandusky, J.M. MamheUo, R.M. Baucom and N.J. Johnston,Proceedings 24th International SAMPE Technical Conference, Toronto, October 1992.

"Issues in the Use of Powder-Coested Towpmg for Textile Application," M.K. Hugh, J. M.Marchelio, and N. Johnston, FIBER-TEX "92, Drexel University, Philadelphia, PA, October1992.

"Customized ATP Towpreg," D. Sandusky, J. Mamhello, R. Beucom, and N. Johnston, 24th

International SAMPE Technical Conference, Proceedings, p. 591-605, Toronto, October 1992.

"ATP Towpreg Architecture Optlmiza_n," D. sandusky, J.Marchello_R. Baucom, and-N.

Johnston, 10th Thermoplastic Matrix and Low Cost Composites Revlaw, San Diego, February1993.

--. • '.. • • o,. .: .• • .

"Powder Curtain Prepreg Process," R. Baucom and J. Marchello, 38th International SAMPE

Symposium and Exhibition Proceedings, p. 1902-1915, Anaheim, May 1993.

"A New NASA LaRC Multi-Purpose Prepregging Unit," S. Wilkinson, N. Johnston, D. Dixon and

J. Marchello, 38th International SAMPE Symposium and Exhibition Proceedings, p.1-15,Anaheim, May 1993.

"Powder Impregnating Advanced Polymeric Materials for Textile Applications," N.J. Johnston, J.T.Hartness, J.D. Muzzy, J.M. Marohello, and M.K. Hugh, NASA 4th Advanced CompositesTechnology Conference, Salt Lake City, June 1993.

"Textile Composites from Powder-coated Towpreg: Role of Bulk Factor DudngConsolidation,"M.K. Hugh, J.M. Marchelio, R.M. Baucomand N.J. Johnston, 25th InternaliormlSAMPE TECH. Conference, Proceedings, p.812-822, Philadelphia, October 1993.

"Composite Material Impregnation Unit" S.P. Wilkinson, J. Mamhelio, and N.J. Johnson, NASATechnical Memorandum No. 107751, December 1993.

"Polylmide Composites from Hot-Meit Prepreg Tape Using Powder Coated Towpreg," S.P.wilkinson, N.J. Johnston and J.M. Marchello, 39th International SAMPE Symposium,Proceedings pp. 905-916, Anaheim, CA, Apdl 1994.

"Towpreg Ribbon Bonding Kinetics," J.A. Hinklay, D.C. Working and J.M. Marchaiio, 39thInternational SAMPE Symposium, Proceedings pp. 2604-2611, Anaheim, CA, Apdl 1994.

"Powder Curtain Process for Fiber Bundle Impregnation," R.M. Baucom, M.K. Hugh and J.M.Marchello, 39th Intemationai SAMPE Symposium, Proceedings pp. 793-801, Anaheim, CA,April 1994.

"Textile Composites from Powder.Coated Towpreg: Yam Treatment for Braiding," M.K. Hugh,J.M. Marohello, J.T. Hartness, S. Goodwin, J.G. Shukla and N.J. Johnston, 39th InternationalSAMPE Symposium, Proceedings pp. 551-559, Anaheim, CA, Apdl 1994.

"Ribbonizing Powder-Impregnated Towpreg," D.A. Sandusky, J.M. Marchelio, N.J. Johnston andR.M. Baucom, 39th intemationai SAMPE Symposium, Proceedings pp. 2612-2626, Anaheim,CA, April 1994.

"Powder Curtain Prepreg Process," Robed M. Baucom and Jospeh M. Marchelio, Journal of.Advanced Materials, Vol_ 25, No. 4, pp. 31-35, July 1994.

"Recent Studies in Langley's Powder Coating Technology,"M:K. Hugh, J.M. Marchello, R.M.Baucom and N.J. Johnston, NASA/DOD ACT Conference, Seattle, WA, August 1994.

"One Step Consolidation of Powder-Coated Composite Preforrns," E.S. Welser, R.M. Baucom,J. Snoha, M.K. Hugh and J.M. Marchello, 26th Intematlonal SAMPE Technical Conference,pp. 462-474, October 1994.

"Micro-Extruder for Polymer Characterization," D.C. Worklng, J.M. Marchello and T.L St. Clair,

26th Intemational SAMPE Technical Conference, pp. 700-714, October 1994.

. .... ", o ." .. •o • _ ° o o.'

Patents

Baucom, R.M., Snoha, J. and Marchello, "Process for Application

of Powder Particles to Filamentary Materials", U.S. Patent No.

5,057,338, October 15, 1991.

Sandusky, D.A., Marchello, J.M. and R.M. Baucom, "Non-Rectangular

Towpreg Architectures and Required Manufacturing Procedures",

U.S. Patent No. 5,405,683, April ii, 1995.

Patent Appliaations

Hinkley, J.A. and Marchello, J.M., "Apparatus and Method for

Determining the Mass density of a Filament", U.S. Patent

Application LAR 14879-I-CU, Submitted May ii, 1992.

Baucom, R.M., Marchello, J.M. and Snoha, J. "Method for

manufacture of Fibrous Composite Towpreg by Powder Curtain Feed

Method", U. S. Patent Application LAR 14926-I-CU, Submitted

May 13, 1992.

Wilkerson, S.P., Johnston, N.J. and Marchello, J.M. "A Dry

Process for Making Uni-Tape Prepreg from Powder Coated Towpreg",

Patent Application LAR 15114-I-CU, Submitted August 31993.

Sandusky, D.A. and Marchello, J.M., "Composite Prepreg Robotic

Consolidation Device", U.S. Patent Application LAR 15259-I-CU,

Submitted March 17, 1994.

United States PatentSandusky et al.

[19]

IllllIInlIIIlIIIIIlUMIInalIlUlIIIIIOIIHIlIIIfllIIIHIIIIIIIINllUS005405683A

[II] Patent Number: 5,405,683

[45] Date of Patent: Apr. 11, 1995

[54] NON-P.X_ANGUIAR TOWPREGAgCm'll_/73g_

[75] Inventors: Donald A. Sssdm_, W',Jlismsb_g;Josh M. _ Hampton;Robert M. Bueom, Newport News,all of VL

[73] xss_e_. TheUuttadStstmotAmmatmrqa.esatad by tltt AdmlaisUat_ of "tim Nstioasl Aeroumics sad SpaceAdmhdJ_oa, Wmhington, D.C.

[21] AppL No.: 141,293

[22] Filed: Oct. 2O, 1993

[51] fat O,. ............................................. B32B 9/00[52] US. CL ................................... 428/225; 428/102;

428/105; 428/232; 428/235; 428/286; 428/294;,428/295

[58] Field of _ ............... 42S/225, 295, 235,428/102, 10S,286, 232, 294

pGj _ OtedU.S. PATENT DOCUMEHTS

5,296,064 3/1994 Muggy et al ................. 156/180

OTHER PUBLICATIONS

Fah'falNorthern Virginia Sun (FHVS) Apr. 5, 1979 p.8.

Primary F_amlner--Patrick J. RyanAni_ant F.xaminer.--Abraham BahiaAttorney,AFe_ or F/tin--George F. H_ Joy L.Bryant

[_'_ ._n'Rxcr

A shaped towpreg n_n having • croes4ection_ ge-ometry which promotes intimate lateral contact be-tween adjacent c0mpomte unn was prepared. Theorca-seztiontl geometry is non-_ and pro-motes intimate lateral oontaot between adjacent tow-preg ribbons during normal processing.

3 agtm, 2 Draw_ Sbem

U.S. Patent Apr. 11, 1995 Sheet 1 of 2 5,405,683

IA.

H3

u.

a_r_

m

LL

'bg

• ".oo°

.': . ..o.

U.S. Patent Apr. 11, 1995 Sheet 2 of 2 5,405,683

ROLLER SURFACEi i

FIG. 2

1

NON-RKCTANGULARTOWPR]_ARCT_13_rURIm

5,405,683

ORIOIN OF THE INVENTION

The invention &sen'bed henfia was made by an e_-ployee of the United Smtm Government and two con-tract employees in the performance of work underNASA Grant Nmnbers NOT $1008 and NAG 1067 and I0

is subje_ to the prow of Pttblk: Law 96-5|7 (3_U.S.C. 202) in which the contractors have elected notto retain title.

CROSS-REFERENCE TO RELATED 15APPLICATIONS

spplka_o, isrelatedtoco-_ l_em appli-cationSet. No. 08/141292, filed Oct. 20, 1993, entitled

"Apparatus for Frovidi_ • Uniform, Consolidated, 20U_ Concinuo_ F1b_Rcinforoed Poly-

meric Material and Method Rekti_ Thereto".

BACKGROUND OF _ I_VSNTION

I.FiekioftheInvention

The present invention relates 8enerally to preprqn3_ms. In particular, it relates to prepre8 n'bbon formswhich have non-rectangu_ architectere_

2. Description of the Rekted Art 30Ribbonized preprqg is used in the automated place-

ment procemt where ribbcms are robotienlly mm_gedand continually fed onto a tool or part ran'face mad ad-hered by application of heat mad pressure. This auto-mated placemmt process is _y semi•ire to 35ribbon nmcet_ q_liW when _S knv.flowmatrix nmteriak. The simultaaeom nmmbly of edja-cent n'bbom (t_icdy 4 to 34) offers _niflcant ad-

vances in the lay-up of cmnpmite preprei_ The low- 4Oflow matrix materials (which age arm high perfor.mance) combined with lack of ribbondimemlonal intel_ity, and most importantly, thetence of the standard _ctanlu_ _ compli-cates the automated placement _ frequently ten- 45dering poor _tL Although ribbmm m boaded totheir vertical _ (direcey below) u_i,k_n3y,the failure to make quality parts is gemnlly attribmedto the poor boadin$ of 8djacent ribbom to esch _her. 50Low-flow thennOl_ parts med_ by _ slit i_-preg mpa are gypicatlly unooa_lidst_ told_e pormity and void content. High to moderate-flow mauix prepreg tape8 and n_obom _ pro.vide well comolidated, void-flee parL This conw._g 55can be mributed to the coaectinlg melt-flow natare ofthe high-flow num_ wh/ch allows forcougregation end filament _ of nazhbor_n'bbons.

60An object of the present invmttion is to ps_A_le a

prepreg z/bbon having a _omd geoatetrywhich promote, intimate lateral contact between adja-cent composite •owl

Another object of the present inveatkm is to prepare 65a compoe/tefrom thepr_rq n'ebom hav/nigthe afore.mentioued t_-try.

2

SUMMARY OF THE INVENTION

The objects of tim, pt'e_at inventioa were met byprovidins • _.iqbbon having •

5 geometry which promotes ine,...mlateralconU,ctornesting betwan 8djscent tows. The _ hm ap_ae o_ comct w_ch pmvi_ in_ of join_upon normal proeem_. Bzamplm of such crmHec-•ion inclede a triaai_ a tmpezold, a pamllelollmm, sad• polyson haviag more than 4 sides. P._mtially, anyshape w_l meet the objectives of the inventioa zs kmlgas it is not rectmlgtdsr m"circular mtd allows for nestingof the n'bbom upon oonmlidatlo_

BRIEF D_ON OF THE DRAWINOS

PIG. IA is a dis_am of the triangular _geometry.PIG. IB b • diasramofthel_mllelogr_ crom-m_

tiontlseometry.PIO. lC is a diasn_ of •ha _ seometry

for • polYlgOa having more than 4 sides.FIG. ID is • diaSram of the uape_idal

tional 8eometry.FIG. 2 is • diqwam of the i_eping and aiilmment of

25 the n_obon_

DESCR/Fr[ON OF _ PREFER.REDEMBODIMENTS

._t a measure of the capsbilit_ of the curreat tech-nology, a low-flow hot-melt prepreg tape Was slit into tinch _ n_ons and mbotically placed onto atoolsurface.F_ • roboticin-situmaneftcturinsprocessknown to tbme skilled in the art, a fiatpanelsection was In'educed. The panel was placed into anautoclave aud processed under v_cuum, pressure andbest. The resultinj panel contained adjacent ra_oaovedal= sad Saps. Mechanical testing proved tim part

A low-flow,12 K, powder coated towpreg washeated and shaped into• non.rmtangular crm.-.eo.tional arab/tee•me. _ was achieved by continuomly

the0ow6_ mated towpresthrou_2_• form_means where• thetowpw4 was consolidatedand pie.

into • wide, fiat, _ form. Uponeziea8 ths femiaS me,a_ the towpreS w_ _li-_ inm a _ wide, flaC =<m-.eceon_ fomand passed into a shaping menm. The shaping meam

ptepreg materk/into • _ havins • non-

mine pmcms am that which was _ for the slittal_a_ l_rtwas _ted. The partwm wenconsolidated.

W]satisclsinmdasaew and desiredtobe securedbyLettersPamnt of•ha UnitedSt•U= is:

L A shapedto_q_rellribbonhavinz a crosHectien_f_smm7 whi_ immm_s intimatelamml o_msct be-twsm adjsceat towprell n'bbom having a similar c_m-seceoeal 8eoate_ wherein the _ i_.try is xlected from the Stoup comis_ag of: a trimq_e, atrapezoid, • pmallelogram, and • polygon havin_ morethu 4 _tm.

• The Japed towwes n_boa a_ording to daim 1,whemin tlm _ 8emaeuy is a _

s. A eempm/te prepared from the shapedn_ w,mrdiag to claim 1.

$ _t 41 8 $

#-.

6

t