The markets: Automotive (2019)

As the global auto industry hurtles toward its confrontation with US fuel economy and European Union (EU) emissions standards in 2017, the pressure built to find more radical solutions to lightweighting.

The automotive industry continues to develop composites for lightweighting vehicles, driven by fuel economy and emissions regulations:

  • Current US corporate average fuel economy (CAFE) standards mandate a fleet average of 54.5 mpg (23.2 km/L) by 2025 (Editor’s note: The Trump Administration has proposed to reduce the US CAFE standards; his proposal, at this writing in early October 2018, is in the public comment phase.);
  • China’s Corporate Average Fuel Consumption (CAFC) sets a fleet target of 20 km/L by 2020
  • EU emissions regulations mandate a mere 95 g/km of CO2 by 2021, with another 15% reduction by 2025, and in 2030, a further 30% reduction from 2021.

The market for carbon fiber in automotive applications was estimated at more than 7,000 metric tons (MT) per year by Chris Red of Composites Forecasts and Consulting LLC (Mesa, AZ, US) at CW’s Carbon Fiber 2017 conference, with more than 100 models currently specifying carbon fiber-reinforced plastic (CFRP) for OEM components. He projects this market will grow to almost 11,000 MT by 2025.

China is now the number one automotive market, with 300 million cars on the road (vs. 270 million in the US) and production of 24.8 million vehicles in 2017, compared to 11.2 million in the US, 8.4 million in Japan, almost 5.7 million in Germany, and 4 million and 3.7 million in India and South Korea, respectively. Thus, it isn’t surprising that development of composite structures used in actual series production vehicles — not just high-end options or concept/prototype models — is being led by Europe and Asia. Composites development announcements in China in 2018 included:

  • Magna Exteriors formed a joint venture with GAC Component Co. Ltd. (GACC, Guangzhou, China) to begin production of thermoplastic composite (TPC) liftgates for a global automaker's crossover vehicle starting in late 2018.
  • Kangde Group (Hong Kong) entered an agreement with BAIC Motor to build an Industry 4.0 smart factory in Changzhou to produce CFRP car body and other components beginning in 2019 and scaling to 6 million parts/yr — its 66,000 MT/yr carbon fiber facility in Rongcheng will begin production in 2023;
  • HRC (Shanghai, China) commissioned the first Rapid Multi-injection Compression Process (RMCP) automated composites production line from Carbures (El Puerto de Santa María, Spain);
  • Volvo’s new, separately branded electric high-performance car company Polestar will start production of its first model, Polestar 1, in 2019 in the new Polestar Production Centre in Chengdu.

That said, 2018 saw the unveiling of the industry’s first carbon fiber composite pickup box, by General Motors (GM, Detoit, MI, US). The first-ever composite bed for a full-size truck was actually built by GM in 2001, but the take-up rate on the Silverado and Sierra Pro-Tec box option was only 10% of what GM expected. Thus, it waited more than 15 years to try again. The CarbonPro pickup box, again an option, but for the 2019 GMC Sierra, was developed with Teijin Automotive (Tokyo, Japan), which acquired Continental Structural Plastics (CSP, Auburn Hills, MI, US) in 2017. CSP has years of experience manufacturing composite boxes for the Honda Ridgeline and Toyota Tacoma trucks, both made from chopped glass fiber sheet molding compound (SMC). The first-generation Honda bed was 30% lighter than steel when it debuted in 2005, but its 2017 update switched away from SMC in two of the components, opting for a direct long-fiber thermoplastic (D-LFT) for the sidewalls and headboard and for a short-fiber compound for the spare tire tray, both injection molded using glass fiber and polypropylene (PP). The 2019 GMC CarbonPro box will also use thermoplastic composites, opting for Teijin’s Sereebo process, which combines a mat of 20-mm-long carbon fibers with a nylon 6 thermoplastic that is compression molded for part cycle times of 60-80 seconds.

This growing trend toward use of thermoplastics in automotive composites is aided by processes such as overmolding, where blanks made of woven or unidirectional fibers in a thermoplastic matrix — known as organosheet — are compression molded into a 3D shape while reinforced plastic is injection molded on top and around to form complex-geometry ribs, bosses, inserts and attachment points. One example is a production Porsche 918 Spyder brake pedal made using a glass fiber/polyamide (PA) organosheet overmolded with a 60% long-glass fiber PA6 compound. Other parts in development or production include seat backs, seat rests, backseat load-through components, airbag housings, B pillars, door cross beams, bumper beams and large floor components.

Another trend is the growing use of unidirectional (UD) tapes to reduce waste vs. woven or noncrimp fabric (NCF) reinforcements. Because the tapes can be cut and placed precisely, very little scrap is produced. The most notable example in 2018 was the CFRP rear wall for the Audi A8 luxury sedan made in a fully automated, Industry 4.0 production line by Voith Composites (Garching, Germany). Offering a 50% weight reduction vs. 3-5 welded aluminum parts and providing 33% of the drive cell’s torsional stiffness, the rear wall begins with Zoltek (St, Louis, MO, US) 35K carbon fiber. It is spread into bindered, 50-mm-wide, UD tape which is then cut to various lengths and applied at specified angles on a rotary table to form a tailored blank, all in a single machine — the Voith Roving Applicator. The blank varies from a base of six plies up to 19 plies where local reinforcement is added, and a thickness of 1.5-3.7 mm. It is then shaped into a 3D preform in a heated press supplied by FILL (Gurten, Austria) which adapts the pressure applied as it stamp-forms separate regions of the preform clamped in the forming tool made by ALPEX Technologies (Mils bei Hall, Austria). The completed preform is then injected with resin and press-molded using the Audi-developed Ultra-RTM process, which uses less than 15 bar of pressure vs. 140 bar common for high-pressure RTM (HP-RTM). Thus, only 350 kN of press force is needed vs. 2,500 for HP-RTM. Although the VORAFORCE 5300 epoxy resin cures in 90-120 seconds at 120°C, the total part cycle time is 5 minutes.

Another alternative to HP-RTM is wet compression molding (a.k.a., liquid compression molding), which does use snap-cure resins and NCF but also lower pressure. Instead of injecting resin into the preform, automated equipment spreads resin over the fabric and then transfers this into a thermoforming press. Eliminating the preforming step and offering cycle times less than 90 seconds and less-expensive equipment, BMW has predicted a significant increase in wet-pressed parts. Huntsman Advanced Materials (Basel, Switzerland) has developed a next-generation process called dynamic fluid compression molding (DFCM) which claims fiber volumes up to 65% and the ability to mold more complex geometries.

For exteriors, ultra-lightweight SMC continues its push below 1.0 g/cc and carbon fiber is also gaining ground, with Polynt-Reichhold (Scanzorosciate, Italy), Aliancys (Schaffhausen, Switzerland) and CSP all adding new SMC production lines over the past few years which have the ability to make carbon fiber SMC. Polynt has also introduced Polynt-RECarbon recycled fiber SMC to its product offerings, as well as UDCarbon and TXTCarbon compounds featuring unidirectional and fabric reinforcements, respectively. The potential for these products can be seen in the front subframe development project completed by Magna International (Aurora, ON, Canada) and Ford Motor Co. (Dearborn, MI, US), which uses locally reinforced and co-molded chopped carbon fiber SMC with patches of SMC made with carbon fiber 0°/90° NCF. This SMC structural subframe must handle significant loads, supporting the engine and chassis components, including the steering gear and the lower control arms that hold the wheels. Though only a development part, it achieved an 82% parts reduction, replacing 54 stamped steel parts with two compression molded composite components and six overmolded stainless steel inserts, while cutting weight by 34%.

Hybridizing SMC with prepreg is an approach used this year by Ford’s global Research and Advanced Engineering group teamed with its Chassis Engineering group in the UK to redesign a production steel suspension knuckle for a C-class vehicle. By co-molding layers of woven carbon fabric prepreg with chopped carbon fiber SMC, a complex-shaped, high-performance suspension knuckle was produced with a cycle time of less than 5 minutes and a 50% weight reduction. Other developments include Saint Jean Industries (Saint Jean D’Ardières, France) and Hexcel (Stamford, CT, US) developing a hybrid carbon fiber/aluminum version of a performance car suspension knuckle, which increased stiffness by 26% vs. an all-aluminum knuckle. Meanwhile, Williams Advanced Engineering (Grove, Oxfordshire, UK) has developed a CFRP wishbone that uses unidirectional carbon fiber and recycled carbon fiber nonwoven mat — up to 80% of the composite part, by weight — to cut weight 40% vs. conventional aluminum versions, yet its cost is comparable to aluminum forgings. The part molded is in 90 seconds using an HP-RTM process called RACETRAK for a 5-minute total cycle time, including layup.

Other trends to watch include CFRP wheels for production models — once production cost and cycle time can be sufficiently reduced — and continued development of hybrid composite-metal components.

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