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TOBIAS PFEFFERKORN ET AL.

The trend towards lightweight con-struction – especially in the mobili-ty sector – is opening up a wide field

of application for engineering plastics insemi-structural and structural parts. The

high mechanical property requirementsfor such components can, however, nolonger be met by short and long glassfiber-reinforced plastics alone. Continu-ous fiber-reinforced plastics – which havebeen used in, for example, the sportsequipment and aerospace sectors formany years – offer a considerable increasein mechanical property values and ener-gy absorption capacity here. But wideruse of continuous fiber-reinforced plas-

tics will be contingent on the ability toprovide economic processing with fast cy-cles similar to those in injection mold-ing, especially in automotive applicationsbecause of high volumes and immenseprice pressure. This is where thermoplas-tic-based fiber-reinforced composites canexploit their strengths over thermosettingmatrices. Thermoplastic-based compo-nents also score in terms of repairabilityand recyclability.

© Carl Hanser Verlag, Munich Kunststoffe international 12/2013

From Laminate to ComponentContinuous Fiber-Reinforced Thermoplastics. Because of their great potential

for lightweight construction and recycling, continuous fiber-reinforced

thermoplastics are rapidly gaining importance. Especially in auto manufacture, the

replacement of metals by thermoplastic laminates is set to continue thanks to their

good mechanical properties combined with efficient processability by injection

molding. Here, with its new product and service package, BASF offers not only

tailored materials but also comprehensive simulation, testing and processing

know-how.

The multifunctionalcomposite demonstratorpart can be produced inone operation (figures:

BASF)

Translated from Kunststoffe 12/2013, pp. 94–100Article as PDF-File at www.kunststoffe-international.com; Document Number: PE111540

COMPOS I T E S

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Complete DevelopmentPlatform

Large-scale production processes suitablefor continuous fiber-reinforced -thermo-plastics have often not yet been optimizedand pose a special challenge for manyplastics processors. For this reason, BASFSE, Ludwigshafen, Germany has now ex-panded its activities in the area of engi-neering plastics to include a completelynew approach. Besides, the conventionalrange of short and long fiber-reinforcedengineering thermoplastics, the compa-ny has recently also started supplying con-tinuous fiber-reinforced laminates andtapes. Under the trade name Ultracom,BASF is offering a package of continuousfiber-reinforced semi-finished products,specifically adapted overmolding com-pounds, and the necessary engineeringsupport.

The basic components of the Ultracomsystem are laminates based on wovenglass (Ultralaminate) and unidirectionalglass and carbon fiber tapes (Ultratape)

impregnated with polyamide. Overmold-ing materials from the Ultramid (PA)range have been specifically developed foruse with these semi-finished products(Table 1). The use of semi-finished prod-ucts often only becomes commercially at-tractive in combination with the conven-tional injection molding process. Withthis approach, the continuous fibers areused only at precisely defined locationswhere high mechanical reinforcement isrequired. Additional functions, e.g. ribsand connecting elements, can then be in-corporated in the component by the over-molding compound. The new UltramidCOM materials ensure optimum bond-ing and load transmission to the semi-fin-ished products.

Processing Expertise withProduction Cell

A key part of the new service package is apilot production cell on which it has beenpossible to produce multifunctional com-posite test components in one operation

(Title figure) since March 2013. The steps oflaminate forming (draping) and over-molding for functional elements are di-rectly combined in a single process and in-jection mold. The production cell makesit possible to expand the company’s ex-pertise and provide optimum support forthe customers in component develop-ment. It is a logical extension of BASF in-house processing facilities.For many yearsnow, numerous special injection moldingprocesses for engineering plastics havebeen trialed and optimized here on 20 in-jection molding machines with clampingforces from 5 to 1,500 t. Similar develop-ment work on extrusion processes for en-gineering plastics has also been carried outon more than 10 extrusion lines, includ-ing a seven-layer film line.

The aim in designing the Ultracomproduction cell was to achieve a fully au-tomated process with typical injectionmolding cycle times. The challenges forprocess and plant design involved:� Parallelizing the individual process

steps,

Fig. 1. Pilot pro-duction cell forthe manufactureof compositesample parts

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Kunststoffe international 12/2013 www.kunststoffe-international.com

Property Ultralaminate B3WG13 WR01

UltratapeB3WG12 UD01

UltratapeB3WC12 UD02

UltramidB3WG12 COM

UltramidB3ZG7 COM

Product characteristicsTwill fabric 2/2 offset,

600 g/m2, 66 wt.-%

GF UD tape, 60 wt.-%

CF UD tape,60 wt.-% PA6-GF60 PA6-GF35

impact modified

Density [g/cm3] 1.82 1.72 1.46 1.72 1.38

Tensile modulus (tr.) [GPa] 22 33 102 20 9.3

Tensile strength (tr.) [MPa] 450 770 1,800 250 145

Table 1. Properties of the Ultracom range: semi-finished products and compounds


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� achieving short laminate heating times,� attaining short and reproducible trans-

fer times from the heating station tothe mold,

� ensuring that the heated, pliable lami-nates can be securely yet gently grippedin a reproducible way,

� exact laminate positioning and fixingin the mold,

� providing the greatest possible flexibil-ity for variations in part geometry andlaminates.

The most suitable concept for a produc-tion cell depends on numerous factors.The main ones are part geometry, size andcomplexity of the laminate, laminatestructure and thickness, method and du-ration of laminate heating, as well asdraping and overmolding times. Thechoice of production cell concept is alsostrongly influenced by the requirementsfor the mold and injection molding ma-chine, necessary plant flexibility, availablespace, investment budget, and number ofunits required.

For easy handling of even the mostcomplex laminates, it is an advantage toheat the semi-finished product close to ordirectly in the draping mold. But in thiscase, carrying out the operations oflaminate heating,draping,and overmold-ing sequentially is a loss in time. If, on theother hand, the laminate is heated out-

side the mold parallel with the injectionmolding process, the cycle time can beconsiderably shortened by parallelprocess steps. In the most favorable sce-nario, the duration of draping and over-molding will determine the cycle time,provided that the steps of heating andhandling the laminate do not take longer.In this scenario, however, the heated, pli-able laminate insert must be transferredreproducibly from the heating station tothe mold. This can be done by needles,(vacuum) grippers, diaphragms orclamping frames.

To provide maximum flexibility andshort cycle times suitable for mass pro-duction, BASF has opted for an externalheating station and a clamping frame forlaminate handling. At the center of theproduction cell built by FPT RobotikGmbH & Co.KG, Amtzell, Germany, is a

six-axis robot (manufacturer: Kuka Ro-boter GmbH, Augsburg, Germany) thatloads the clamping frame, transfers thelaminates to the oven and then to themold, and finally removes the finishedpart (Fig. 1). For these operations, the ro-bot is equipped with a complex gripperthat enables it both to pick up the lami-nate and finished part by vacuum cupsand also fix the clamping frame.

After laminate tailoring by water jetcutting, milling, sawing, laser cutting orultrasonic cutting, the precuts are fed tothe process via a magazine. It is impor-tant to avoid delamination, burrs orjagged edges as well as localized thermaldamage to the edges during the cuttingstep. Processing aids should also bechosen with caution in order not to in-hibit adhesion of the overmolding com-pound.

In order to ensure a constant positionin the mold without costly sensors foreach process step, accurate gripping andprecise placement of the laminate in theclamping frame are essential.A simple butingenious solution is the inclinedarrangement of the laminate magazine.This allows the vacuum cups to pick updifferent laminate shapes and transferthem to the loading station in a repro-ducible way (Fig. 2, left) without the aid ofsensors.

BASF SETrade press office Performance MaterialsD-67056 LudwigshafenGermanyTEL +49 621 60-43348> www.plasticsportal.eu

Contacti

Fig. 2. Magazine, loading station, and mold in the production cell


The clamping frame is designed in twoparts and clamps the laminate viamatched spring assemblies from the timeit is laterally fed into the loading stationuntil active opening in the injection mold.Through the defined clamping of thelaminate in the frame, further handlingin the molten state is greatly simplifiedand the laminate position in the mold isclearly defined. The secure clamping alsopermits rapid robot movements withoutdamage to the laminate, such as wrin-kling. The disadvantage is that the lami-nate is inadequately heated at the clamp-ing points. These points must thereforebe minimized in a defined way that en-sures the laminate is securely clamped inthe frame without compromising drap-ing in the mold.

A second loading station allows thelaminate to be fed manually to enableflexibility in working with different lam-inates and materials.

The laminates are heated by medium-wave infrared heaters from Krelus AG,Oberentfelden, Switzerland. The heaters,optimized for the absorption behavior ofplastics, permit rapid, energy-efficientheating for about 20 to 25 s to around260°C. To prevent temperature inhomo-geneities, due to convection currents forexample, the laminate is positioned hor-izontally in a closed, thermally insulatedoven chamber and heated from bothsides. Temperature measurement andcontrol at the top and bottom of the lam-inate are carried out by specially arrangedpyrometers. An adjusted output regula-tion of the heater zones prevents over-heating and therefore local surface dam-age to the material.

Special attention must be paid to thesubsequent transfer path of the heatedlaminate from the oven to the mold. Ribpull-off tests show the effect of transfertime from the oven to the mold on the

strength of the bond between the lami-nate and overmolding material (Fig. 3). Forthis reason, the transfer time must be keptas short but also as reproducible as pos-sible. With an additional pyrometer inte-grated into the gripper, the temperatureof the laminate during transfer can becontrolled and hence constant insert tem-peratures ensured.

Flexible Mold for DemonstratorPart

The clamping frame is positioned in themold via guidance bars on the movingmold half. As the mold closes, the frameis precisely opened via pins and releasesthe laminate for draping. The mold(manufacturer: Georg Kaufmann For-menbau AG, Remetschwil, Switzerland,see Fig. 2, right) is a key part of the Ultra-com process and was designed to offerhigh flexibility. Through interchangeableinserts, variable leader pins and the useof shearing edges, different geometriesand laminate thicknesses can be accom-modated and the limitations of laminatedraping explored. Via a hot runner sys-tem with six needle shut-off nozzles thatcan be opened independently through acascade control system, individual com-ponent areas can be selectively injected.So the mold is also suitable for highlyfilled, long glass fiber-reinforced moldingcompounds such as Ultramid Structure.In addition, it is equipped with a compre-hensive sensor system to measure pres-sure and temperature at different compo-nent positions. The hydraulic injectionmolding machine used is from Krauss-Maffei Technologies GmbH, München

7 10 s 15Transfer time

120

100

80

60

40

20

0

%

Stre

ngth Fig. 3. Determination

of rib strength as afunction of transfertime in a tensile test

© Kunststoffe

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Fig. 4. The demon-strator part with itsfunctions

© Kunststoffe


(KM 300 1400C2 with 3,000 kN clamp-ing force).

Demonstrator Part with 20 Functions

The laminate is draped to form the car-rier structure shown in the center of thedemonstrator part (see Title figure), beforefurther functional elements are over-molded.Altogether, numerous character-istic features and problems of compositeproduction can be simulated with the360 ×360 mm2 multifunctional part and

its about 20 individual functions (Fig. 4).Besides the ribbed, U-profile carrier, thefeatures of the component include a ribfield for special crash tests, differently de-signed rib/wall thickness transitions ofthe laminate and overmolding material,as well as “sewing points”, i.e. points atwhich the laminate can be through-mold-ed via varying cross sections.

For economic component productionwithout post-machining steps such asedge trimming, defined closure of thedraped laminate edge is necessary.For thisreason, it is overmolded in different vari-

ants: with overlaps on one side, on bothsides or in offset configuration as amounting surface for adjacent componentassemblies. To fix the laminate in the vari-ant overmolded on both sides, holdingbars are integrated into the edge region.The design of the long, peripheral flowchannel proved a special challenge. Theaim was to achieve complete filling of thewhole periphery, including the 0.6 mmoverlapping areas – even with the 60 wt.-% glass fiber-reinforced grade UltramidB3WG12 COM. To meet this challenge,not only draping but also subsequent fill-

Fig. 5. CT scan ofmounting holes in different materials

© Kunststoffe

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Mold closing/draping of laminate

Melt injection

Cooling and dosing

Mold opening

Removal of part and frame

Part deposition &frame transfer to insertion stationInsertion of laminate intoclamping frame

Frame transfer to turning station

Frame transfer into IR oven

Heating of laminate

Frame transfer into mold

Holding of temperature

Frame 1

Frame 2

Frame 3

110 s 55 sFig. 6. 50 % reduction incycle time by paralleliz-ing process steps

© Kunststoffe


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ing with the overmolding material weresimulated (Title figure) and the gate posi-tions and opening sequence of the needleshut-off nozzles optimized.Following tar-geted modification of highly filled Ultra-mid B3WG12 COM, the required fillingpressures are not substantially more thanfor the impact modified 35 wt.-% filledvariant Ultramid B3ZG7 COM.

Finally, typical mounting elementssuch as circular recesses of different di-ameter are incorporated in the compo-nent. They can be created by opening outthe fiber bundle during draping or sub-sequent punching directly in the mold. Inthe first option, needles are advanced asthe mold closes and pierce the laminate,laterally displacing the fibers. A comput-er tomography scan of the componentduring in-house testing shows visible ev-idence of the advantage of this process-ing option, which is gentler on the fibers.The scan provides a ready basis for fur-ther optimization of the needle move-ments (Fig. 5).

The fully shaped and overmolded com-ponent and the empty clamping frame arethen removed by the six-axis robot fromthe fixed mold half. The clamping frameis then ready for re-loading.

If the process is run with a high degreeof parallelization, three clamping framesare used simultaneously. While the firstclamping frame is in the injection mold-ing machine, the second holds the lami-nate in the IR oven, and the third is re-loaded by the robot (Fig. 6). In this way, cy-cle times of less than a minute can beachieved, corresponding to those of astandard injection molding process. Con-

sequently, a key requirement for the useof this process in large-scale productionhas been fulfilled.

Complex Draping SimplyAchieved

While it is relatively easy to assess the dra-pability of the Ultracom laminate to forma straight U-shaped carrier, componentswith more complex (especially asymmet-rical) draping geometries pose consider-ably greater challenges for componentdesign – as the rear seat back made fromUltralaminate in Figure 7 shows. It is there-fore important to clarify at an early stageof the project the key question as towhether wrinkle-free draping is possible.The next step is then to determine thenecessary laminate geometry. Drapabil-ity and laminate precut geometry have acrucial influence on overall mold andprocess design, e.g. on the requiredpositioning of the needles and leaderpins.

A typical, practically relevant design el-ement for stiffening flat components isthat of stiffening corrugations. In the Ul-tracom test mold, a corrugation is there-fore incorporated at an angle of 30° to thefeed direction of the laminate. Throughthis offset arrangement,possible fiber dis-placement in the individual layers of the1.5 mm thick Ultracom laminate can bedetected. As Figure 8 shows, a 70 mm ×20 mm corrugation can be formed withhigh quality and precision. Besides beingvisually assessed, fiber orientation was al-so analyzed in a computer tomographyscan and compared with the draping sim-ulation of the component area. The highcorrelation between the simulation-based


Fig. 7. Rear seat back as an exam-ple of complex draping geometry(manufacturer: Johnson Controls)

Fig. 8. Corrugation formation: comparison between CT scan and draping simulation

Fig. 9. The demonstrator part with angled L-profile carrier


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and the measured fiber orientations pro-vides a basis for making highly accuratepredictions of the mechanical propertiesof continuous fiber-reinforced compo-nents.

The second test geometry selected wasan asymmetrical L-profile carrier, whoseshort arm is slightly angled at the end.Higher degrees of draping, sharp edges,and small radii pose a particular challengefor laminate forming here but can be ac-complished cleanly and wrinkle-free withUltralaminate (Fig. 9). Besides draping, an-other task in producing the L-profile car-rier was to achieve a rectangular edge fin-ish, which, as with the straight carrier,could be overmolded all round with a5 mm wide edge. On the basis of the lam-inate determined in the draping simula-tion, it was possible to implement thisgeometry successfully without tedious it-eration steps. This reliable prediction,even of complex draping processes, is akey advantage of the Ultrasim simulationtool, which helps avoid multiple adjust-ments of the clamping frame geometry ordamage to the shearing edges by locallyoversized laminates.

Processing of Ultratape andNatural Fiber Mats

Besides handling, draping and overmold-ing of impregnated fabrics, the use of uni-directionally reinforced tapes is often ofgreat interest. The two continuous fiber-reinforced semi-finished products fulfilldifferent functions in the component.While thermoplastic laminates are moresuitable for large, quasi-isotropicallystressed hybrid components, tapes areparticularly good for local, stress-opti-mized reinforcement of injection mold-ed, short glass fiber-filled components.

Here, they can fully exploit their advan-tage of undulation-free orientation.There is no additional fiber deflection,like in fabric laminates, and the fibers canspecifically follow the load path.

Tape inserts can be constructed in verydifferent forms and vary in handling dif-ficulty according to their layer structure.To build up processing expertise in thisarea, too, tape structures were processedin the Ultracom production cell and char-acterized. Both homogeneous sheets withfiber orientations of 0° and 90° and sym-metrical 0°/±45°/90° combinations wereused. During heating in the IR oven andsubsequent forming, the Ultratape struc-tures were stable in all cases. Overmold-ing was also possible without separationof the tape layers (Figs. 5 right and 10 left). Sta-bility is naturally greatest with combinedstructures, while unidirectionally orient-ed tapes can be partially displaced by theinjection pressure. So, once again, in ad-dition to careful selection of the tapestructure, determination of the most suit-able gate positions and injection param-eters using Ultrasim is recommended.

Other materials, such as thermoplas-tic, Acrodur-bonded natural fiber hybridnonwovens can also be pressed and over-molded in one operation in the novel pro-duction cell (Fig. 10, right). In this way, mul-ti-functional, ready-to-use componentswith new properties in terms of weight,appearance, and recyclability can be eco-nomically produced.

Conclusion

The challenges in terms of weight saving,cost efficiency, and performance encoun-tered in the production of thermoplastic-based fiber-reinforced composites canonly be solved by taking into account the

interaction of all relevant factors. Here,the availability of the material portfolioand application development with simu-lation, processing, and test laboratory fa-cilities under one BASF roof makes it pos-sible to provide support for customersthroughout the process chain from ma-terial characterization to the launch offull-scale production. In the manufactureof complex composite components, it isparticularly important for automatedprocesses to become available in the nearfuture so that widespread market pene-tration can be a tangible reality. The newproduction cell is therefore a key elementin the successful development of highlyefficient composite components.�

THE AUTHORSDR.-ING. TOBIAS PFEFFERKORN is a Processing

Technologies Specialist in the Business Unit Engi-neering Plastics Europe of BASF SE, Ludwigshafen,Germany.

PROF. DR.-ING. REINHARD JAKOBI is Head of Pro-cessing Technologies in the Business Unit Engineer-ing Plastics Europe of BASF SE, Ludwigshafen.

DIPL.-ING. (FH) ANDREAS NIXDORF is a Process-ing Technologies Project Engineer in the BusinessUnit Engineering Plastics Europe of BASF SE, Ludwigshafen.

Fig. 10. Sample parts produced from tapes and natural fiber nonwoven

Collections of articles about specific topics (construction, automotive, electri-cal/electronics, packaging, medical, temperature control) can be found atwww.kunststoffe-international.com/dossiers

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