Recent Developments in High-Performance Thermoplastic Composites Allan Murray, Ecoplexus Inc. Klaus Gleich, Southern Research Institute ACCE 2003

Overview Introduction Materials Process Technology Applications

Why Use Composite Materials ?

Thermoplastic Composites Benefits Unique properties Vibration dampening Light weight Potential for low cost Shelf life Recyclable Durability Fatigue Corrosion Toughness Limitations Cost Materials Manufacturing Tooling Design know-how Manufacturing know-how Use temperature

Thermoplastic Composites Many Polymer Options Polyethylenes Polypropylenes Nylons Polycarbonates Acrylics Polyesters Polyimides Polysulfones Polyketones Polyurethanes the list continues Many Property Options ultimate strain > 100% no microcracking no delamination dampening no water uptake low dielectric properties melt formable weldable elastomeric - plastic - elastic behavior the list continues

Cost Challenge

High-Performance Thermoplastic Composites Properties are fiber dominated Oriented long or continuous fiber reinforcement High volume fiber fraction (up to 65% by volume) Key benefits: Reducing thermal limitations (e.g. creep) caused by the TP matrix system Reducing costs and weight and retaining toughness, formability, weldability, short cycle times, recyclability benefits of the thermoplastic matrix

Thermoplastic Materials

Commercial Materials GMT (Glass Mat Reinforced Thermoplastics) Pultruded Products LFT (Long Fiber Reinforced Thermoplastics) CFT (Continuous Fiber Reinforced Thermopastics) Wire coated products Commingled fibers Powder coated materials Film sticking Slurry processes

Long-Fiber Thermoplastic Composites New Hot-melt Process Produces Fully Wet-out Composite Products Wide Range of Polymers and Fibers Continuous Tape and Rod Products Discontinuous Products with Any Fiber Length Glass Products <$1.00/lb Carbon Products <$8.00/lb

Pilot Production for Thermoplastic Composites

Short Fiber, Long Fiber and Continuous Fiber Composites Typical short fiber thermoplastic material, granules with fiber length of approx. 2 to 4 mm, resulting fiber length in a part of approx. 0.4 mm Long fiber thermoplastic material, pellets of ½” and 1 “ fiber length, resulting fiber length in a part of approx. 4-6 mm in injection molding and approx. 20 mm in compression molding Continuous reinforced thermoplastic material, tape used for woven sheets (thermoforming), filament winding or pultrusion

Typical Pultruded Prepregs Fiber: E-glass, S-glass, Carbon, Aramid, polymer fibers Matrix: PE, PP, PA (6, 6/66, 12, …), PET, PBT, PC, PEI, PPS, SMA, blends, … Fiber content: 20% - 60% standard, some up to 84% Product forms: Tape, pellets (0.5”, 1”), woven tapes more complex textile structures in development

Twintex - The Commingling Concept Consolidated Composite Twintex® Prepreg Temperature + Pressure Source: Vetrotex

Twintex – The Commingling Concept E Glass adapted sizing Plastic filament Additives : - coupling agent - UV stabilizer - natural or black Source: Vetrotex

Twintex – The Manufacturing Process Extruder Bushing TP Glass Commingling Roving Source: Vetrotex

Twintex - Commingled Fiber Products Fiber/matrix combinations: E-glass/PP, E-glass/PET Fiber content: 60 % and 75 % by weight Product forms: Roving, fabric, pellets Twintex Limitations: Matrix material must be usable for a fiber spinning process  limitations in MFI/viscosity, additive type and additive content

Physical Property Data Vetrotex Twintex Source: Saint-Gobain Vetrotex, “Twintex PP and PET Mechanical Properties (non standard)”

Powder Impregnated Prepregs – The Hexcel TowFlex-Technology Fiber Creel Racks Fluidized Bed Powder Coating Chamber Take-up System IR Oven Puller To Weaving To Tapes To Pellets Charged Resin Powder Source: Hexcel

Hexcel TowFlex Typical fibers: Typical resins: Typical product forms: Carbon, E-glass, S-glass Typical resins: PP, PA6, PPS, PEI, PEEK Typical product forms: Flexible Towpreg Woven fabric Braided Sleeving Unidirectional Tape TowFlex Glass Carbon

Physical Property Data Hexcel Towflex Source: Hexcel Composites (March 2003) www.Hexcel.com

Process Technology

Current Composite Materials and Processes

Composite Performance versus Fiber Length Fillers Short Fiber Long Fiber Continuous Source: OCF

The Long Fiber Advantage Stress is transferred to the fibers - the structural members of the composite Long fibers create a “skeletal structure” within the molded article that resist distortion and provide unmatched strength, toughness, and overall performance Source: Ticona

Continuous Fiber Advantage In continuous oriented fibers the load is ultimately ‘fully’ transferred to the fiber As a result tensile creep is limited in fiber direction

Manufacturing Processes for High-Performance TP-Composites Low volume manufacturing processes Discontinuous processes Thermoforming Thermoplastic S-RIM, RTM and VARTM Thermoplastic filament winding Vacuum bag molding Net shape preforming (modified P4)

Manufacturing Processes for High-Performance TP-Composites High volume manufacturing processes Discontinuous processes Injection molding with LFT-pellets and concentrates (high performance resin/fiber combinations) Inline compounding (high performance resin/fiber combinations) Back molding / local reinforcement Compression molding Stamp forming Preheated preforms Matched metal tools Potential to manufacture very thin sections (0.5 to 1 mm) Drapable material required Continuous processes Pultrusion LFT-extrusion

Materials Used For Liquid Molding Processes Cyclics Reactive nylon Fulcrum Requirement for these materials Viscosity less than 3000 mPa.s (cP) (better less than 1000 mPa.s (cP))

Cyclics Cyclic form of PBT, PET, PC and others Only PBT commercial available Based on a ring shaped cyclical form One or two part systems Solid at room temperature – low viscosity resin at elevated temperature (approx. 150 cP) Polymerize into the Polymer using a catalyst Isothermal process Typical process temperature: 180 – 200 oC

Reactive Nylon For more information see presentation on “Reactive Thermoplastic VARTM/RTM/S-RIM”

Thermoformed Fulcrum Components ISOPLAST matrix (Dow proprietary engineering thermoplastic polyurethane) Thermoplastic viscosity issues addressed by ability to reverse polymerization in the melt stage, reducing viscosity to ensure good impregnation Repolymerizes upon cooling, retaining traditional thermoplastic composite advantages High impact resistance Recyclability High elongation to failure (~2.5%, versus ~1-1.5% for thermosets) Zero-emissions processing Fulcrum is the combination of ISOPLAST and pultrusion, with specific hardware design Provides 10-fold line speed improvement over typical thermoset pultrusion lines Allows thermoforming, welding, and overmolding of finished pieces Thermoformed Fulcrum Components Figures from “Fulcrum Thermoplastic Technology; Making High-Performance Composite via Thermoplastic Pultrusion” Dow Plastics, January 2000

Physical Property Data Dow Fulcrum 45v.% and 55v.% data from Matweb.com 76.6wt.% and 66wt.% data from “FULCRUM: Thermoplastic Composite Technology, Making High-performance Composite via Thermoplastic Pultrusion” Dow Plastics, January 2000

Reactive Thermoplastic VARTM/RTM/S-RIM Similar the thermoset process Reaction of at least two components creates a thermoplastic resin that can be melted, pre-shaped, welded, … Low viscosity is required Possible materials: Nylon, TPU, C-PBT (Cyclics)

Problems Connected With Thermoplastic RTM Reaction can be stopped or made incomplete by Moisture Chemicals in fiber sizing Most of the thermoplastic compatible sizings are not developed for such type of processes Availability of compatible sizings in form of fabric is very limited Oxygen Only limited support of material manufacturers Material costs (in case of c-PBT)

Thermoforming Heat in Oven Thermoforming Operation Finished Product

Thermoforming Weight performance: Design flexibility: Processability: Good weight/performance ratio for fabric reinforced sheets due to continuous fibers Reduced weight/performance ratio for extruded sheets depending on the resulting fiber length Design flexibility: Limited, especially for complex geometries Simulation tools available Processability: Stabilization against oxidation necessary Fiber disalignments with continuous fibers possible depending on geometry, material, tooling and process conditions Recyclability: High rate of production scrap (fixation) No direct recyclability Use in other processes like plastication of regranulation

TP S-RIM, RTM, VARTM Weight/performance: Design flexibility: Excellent Design flexibility: Limited to preforming capability, flow length and flow behavior of the resin Processability: Reaction can be sensitive to moisture and fiber sizing Recyclability: Production scrap due to preforming step depending on preforming method No direct recyclability; can be used in other processes

TP Filament Winding Weight/performance: Design flexibility: Excellent Design flexibility: Limited to symmetric parts that can be wound on a mandrel Processability: Higher oxidative stabilization required Recyclability: Low rate of production scrap No direct recyclability Scrap can be used in other processes

Vaccum Bag/ Hand Lay-Up Weight/performance Excellent due to continuous fiber reinforcement Design flexibility Limited to drapability and to the posibility of manually lay up Processability Higher void content due to low pressure consolidation Using autoclave to reduce void content Often fiber disalignments Recyclability High rate of production scrap possible depending on the size of the material sheets and the part geometry No direct recyclability Scrap can be reused in other processes

LFT-Injection Molding Weight/Performance Lower end of thermoplastic composites due to reduced fiber length in the final part Improvements possible by using local reinforcements (using pultruded sections, sheets or tapes of continuous composites  localized strengthening and stiffening, reduction of warpage) Design Flexibility High Flow channels and positions of gates have to be carefully designed Processability Highly stable Recyclability Low production scrap rate Can be reused in the same process

Compression Molding Weight/Performance Design flexibility Medium Retaining fiber length gives excellent properties for a random oriented material, but is lower than using a fabric Local reinforcement or fabric reinforced GMT improve it (using pultruded sections, sheets or tapes of continuous composites  localized strengthening and stiffening, reduction of warpage) Design flexibility High Special simulation tools available Processability Very stable process Recyclability Some production scrap due to trim operations Scrap can be added and reused in the same process (GMT only sheets can be reused in the same process, but not recommended)

Curv Self-reinforced polypropylene Consists of “hot compacted” polypropylene fiber or tape Surface of tape or fiber melts during compaction to form the “matrix” that binds the directional elements together Oriented morphology provides over six-fold increase in tensile strength and nearly 5-fold increase in tensile modulus over isotropic polypropylene, with ~2% weight penalty Nearly doubles tensile strength of 40% random mat short glass polypropylene, with comparable modulus and 22% weight savings Elimination of glass reinforcement has several advantages: Increased recyclability Reduced weight Lower temperatures and pressures for thermoforming Reduced irritation in the workplace High strain to failure, with good impact strength Data from “A New Self-Reinforced Polypropylene Composite” Jones, Renita S. and Derek E. Riley

Physical Property Data Curv from BP document “A New Self-Reinforced Polypropylene Composite” Jones, Renita S. and Derek E. Riley, 2002

Pultrusion Weight/performance Design flexibility Processability Good to excellent due to continuous reinforcement Design flexibility Low design flexibility Limited to constant cross sections, but can be shaped (pull/press) Processability Only limited experience available Depends on stabilization of the material as well as used material form Recyclability Low rate of production scrap expected No direct recyclability Can be used in other processes

LFT-Extrusion Weight/performance Design flexibility Processability Medium weight performance Depends on retaining fiber length Design flexibility Low design flexibility Limited to constant cross sections Can be post shaped or pull formed Processability Not a lot of experience A stable process is expected using the right die design Recyclability Low rate of production scrap Can be reused in the same process

Economics Process Cycle Time Tooling Costs Scrap Rate Overall Economics Thermoforming Medium Low High Good for low volume production with no or limited thickness variation TP S-RIM, RTM, VARTM Medium to long, up to several minutes VARTM: low, single sited tool RTM: low to medium S-RIM: Medium Depends on preforming technique; often high for complex shaped parts Good for low volume production TP Filament Winding Medium to long, depending on number of tapes and heating system Low to medium Good for symmetrical parts in low to medium volume production Vacuum Bag/ Hand Lay-up Long; manual preparation can be hours for a part Low, single sided tool Medium to high Good for prototyping. Not recommended for production scale. Injection Molding LFT ILC Short cycle times; typically 50 – 80 sec. High; steel tools with ejector pins and slides Very low Excellent for high volume production Compression Molding GMT Short cycle times; typically 35 – 60 sec. Low – medium depends on cut outs. Scrap can be reused Excellent for high volume production of large components Pultrusion Continuous process; not enough experience on throughput Limited experience available Extrusion Continuous process; throughput mainly limited by cooling capacity of calibration die Expected to be cost effective for profiles

Applications

Applications For High-Performance Thermoplastic Composites Aerospace and defense: Radomes, wing and fuselage sextions, anti-ballistics Infrastructure and Construction Window profiles, rebar, beams, structures, composite bolts Consumer / recreational Orthotics, safety shoes, sporting goods, helmets, personal injury protextion, speaker cones, enclosures, bed suspension slats Auto and truck Bumper beams, skid plates, load floor, seat structures Transportation Railcar structure, body structure and closures Energy production and storage Oil and gas structura tube, wind turbines

BMW M3 Bumper Beam - Beam and crush columns manufactured using Hexcel TowFlex PA6 Parts welded by high frequency vibrational welding 2 versions: Standard M3 based on glass fiber reinforcement (approx. 40 cars / day) M3 CSL (limited to 1600 total) using Carbon fiber reinforcement Source: Jacob Kunststofftechnik GmbH & Co. KG www.jacob-kunststofftechnik.de

Helmets Military helmet for Norwegian Army Made by Cato Composites 50,000/year TEPEX antiballistic 302 Aramid/PA6 continuous reinforcement Source: Bond-Laminates GmbH www.bond-laminates.com White water helmet Made by Prijon TEPEX dynalite 701 Glas, Carbon, Aramid/PA6.6 Continuous reinforcement Source: Bond-Laminates GmbH www.bond-laminates.com

Aircraft Applications Fixed wing leading edge for Airbus Fokker Special Products/Airbus TEPEX semipreg 107 Non fully consolidated, flexible layers of continuous fiber reinforced thermoplastics Glass/PPS Wing access panel for Airbus Fokker Special Products/Airbus TEPEX semipreg 207 Non fully consolidated, flexible layers of continuous fiber reinforced thermoplastics Carbon/PPS

Mine Sweeper Armouring Made from TEPEX antiballistic 302 Aramid/PA6 Continuous reinforced Made by Kvaerner Source: Bond-Laminates GmbH www.bond-laminates.com

Safety Shoes Composite Toecap History: Newer development: Composite Toecaps were manufactured in the past using GMT with 50% fiber glass content Changing the regulations, this was not sufficient to meet the 200 J requirement Newer development: 65 g / piece (metal 105 g /piece) 200 J resistance Made from Twintex and LFT, 60% fiber glass, PP Manufactured by Security Composites Ltd. (UK)

Others GF/PP composite tank Produced by Covess (Belgium) using Twintex and GMT, welded out of 3 pieces and designed to withstand pressure to 100 bar Evaluation of thermoplastic composite rebars made with the Fulcrum process Thermoplastic composite bolts made by Clickbond Inc. using a thermoforming approach Loudspeaker cones, electronic housings and lightweight carbon fiber reinforced structural applications for the automotive industry made by Centrotec AG Prototype of a continuous fiber reinforced PP boat (JEC 2000 Innovation Award) made from Twintex using vaccum bag molding. Developed by Halmatic, Ltd. Golf club shafts made from PPS/carbon prepreg tape with 66 – 68% fiber content. Multi-step operation including a table rolling, a compression and an oven consolidating step. Manufactured by Phoenixx TPC.

The Future of Thermoplastic Composites Will go to more structural applications using different technical thermoplastics in combination with glass, carbon and synthetic fibers. Will replace metal applications and reduce weight. Improved processing methods will be developed and applied.

Conclusions High-performance thermoplastic composites with fiber-dominated properties are a way to lower cost higher performance short cycle times Recyclability Pre-impregnation can improve wet out and performance over commingled prepregs Materials and manufacturing methods are available

Acknowledgements Aaron Brice and Erik Nolte, Stewart Automotive Research, LLC