An advanced sheet compression molded suspension (ASMC) suspension steering knuckle developed by Marelli. This component was a “Future of Lightweighting” winner for the 2020 Altair Enlighten Awards. Photo Credit: Altair
Composites are used frequently in motorsports and lower volume, high-end/luxury vehicles, which typically favor continuous carbon fiber materials. Growth in both segments from 2021 into 2022 continues. For the more cost-sensitive market of mid- and high-volume production models, composites continue a steady, incremental increase primarily via continuous glass fiber-reinforced polymers (GFRP) in applications such as leaf springs, as well as chopped fiber molding compounds, including sheet molding compound (SMC) body panels and frames, bulk molding compound (BMC) housings and support structures and injection molded thermoplastics for bumper frames, lift gates and seat structures.
According to a Nov. 2019 report by Stratview Research, the top applications for composites in automotive are, in order of volume, underhood components, exteriors and interiors. Another growing market is suspension components and drive shafts. In addition to leaf springs, examples include:
- Hybrid glass fiber composite/aluminum upper control arms for the Ram 1500 half-ton pickup truck, developed by Stellantis (Auburn Hills, Mich., U.S.) and Tier 1 supplier Iljin Group (Seoul, South Korea);
- Rear suspension knuckle developed by Ford Motor Co. (Dearborn, Mich., U.S.) using SMC and prepreg;
- Advanced SMC steering knuckle developed by Marelli (Corbetta, Italy);
- Hybrid carbon fiber/aluminum suspension knuckle by Saint Jean Industries (Saint Jean D’Ardières, France) using prepreg from Hexcel (Les Avenières, France);
- Carbon fiber/epoxy suspension links press-formed over aluminum by Shape Machining Ltd. (Oxfordshire, U.K.);
- CFRP stabilizer bars by IFA Composite (Haldensleben, Germany);
- CFRP wishbones molded in 90 seconds using recycled carbon fiber and the RACETRAK process, developed by Williams Advanced Engineering (Oxfordshire, U.K.);
- Arch-shaped, multifunctional unidirectional (UD) glass fiber/epoxy front axle “blade” that incorporates suspension, anti-vibration/noise and anti-roll;
- CFRP output shaft developed by Dynexa (Laudenbach, Germany).
Rassini rear suspension system for the Ford Motor Co.’s 2021 F-150 pickup truck model. Photo Credit: Hexion Inc., Rassini
One of the most notable suspension structures announced in 2021 was the carbon fiber rear suspension system (above) developed by Rassini (Piedras Negras, Mexico) for the MY 2021 Ford F-150 pickup truck. This highly loaded part is being manufactured by Rassini using resin transfer molding (RTM) to mold a glass fiber reinforcement with Hexion’s (Columbus, Ohio, U.S.) EPIKOTE resin
For exteriors, ultra-lightweight SMC continues its push below 1.0 gram per cubic centimeter (g/cc) and carbon fiber is also gaining ground, with Polynt Composites (Scanzorosciate, Italy), AOC (Schaffhausen, Switzerland) and Teijin Automotive Technologies (formerly CSP VICTALL, Tanshan, China) all adding new SMC production lines over the past few years, all of 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 UD and fabric reinforcements, respectively. The potential for these products can be seen in the front subframe development project completed by Magna International (Aurora, Ontario, Canada) and Ford Motor Co., which uses locally reinforced and co-molded chopped carbon fiber SMC with patches of SMC made with carbon fiber 0°/90° non-crimp fabric (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%.
Another significant driver for composites in automotive is the global push for zero emissions by 2050, which is leading to increased development and production of electric vehicles (EVs). In September 2020, California announced it will require all new passenger cars and trucks sold in-state to be emissions free by 2035. At the same time, the EU proposed its 2030 target, which tightens new car CO2 emissions to 50% below 2021 levels, up from the previous 37.5%. Julia Atwood, head of advanced materials at BloombergNEF, speaking at the IACMI Fall 2020 members meeting, said that by 2025, the average price of EVs is expected to drop below that of internal combustion engine (ICE) vehicles. She forecasts that global sales of EVs will exceed ICE vehicles by 2037 and will reach 50 million units/year by 2050.
The paradigm shift in powertrain technology introduces, on a mass scale, demand for robust battery enclosure systems that can meet stringent mechanical and impact requirements, as well as fire, smoke and toxicity performance to protect vehicle occupants in the event of a battery fire. Further, because battery packs add so much weight to a vehicle, enclosures are also asked to help reduce mass. For all of these reasons, composites are proving highly favorable in battery enclosure applications, and these structures — in cars, trucks, buses and other vehicles — are shaping up to be a major opportunity for composites use in ground transportation.
Battery housing assembled, with cover open. Photo Credit: Evonik
Throughout 2020 and 2021, multiple material suppliers, automotive manufactures and composites fabricators announced battery enclosure solutions for EV use. For example, Evonik Industries (Essen, Germany) reported in February 2021 that it is leading a consortium of partners that have developed a lighter and more cost-effective high-voltage battery housing concept for e-mobility solutions using glass fiber-reinforced epoxy SMC. The holistic battery system concept is designed to offer the automotive industry a safer and more energy-efficient alternative to metals or higher priced carbon fiber-reinforced plastics (CFRP). The consortium includes Evonik, design specialist Forward Engineering (Munich, Germany), battery technologist LION Smart (Garching, Germany), compounder and fabricator Lorenz Kunststofftechnik (Wallenhorst, Germany) and engineering services and business development specialist Vestaro (Munich, a joint venture of Evonik and Forward Engineering) and, most recently, MINTH (Jiaxing City, China), a global manufacturer of EV battery housings and other automotive structures. The composite battery housing concept developed by the consortium can be used for three battery sizes: 65 kilowatt-hours (kWh), 85 kWh and 120 kWh for use in various vehicle sizes and class. CW spoke with engineers from Evonik and Vestaro to learn more about the consortium, the epoxy SMC, the housing design and the consortium’s go-to-market plans.
IDI Composites International EV battery enclosure manufactured with FLAMEVEX. Photo Credit: IDI
In 2020, IDI Composites International (Noblesville, Ind., U.S.) introduced FLAMEVEX, a new family of fiber reinforcements and resins designed specifically for the manufacture of battery enclosure systems for the EV and new energy vehicles (NEV) market. The FLAMEVEX family of products, which include chopped glass fibers combined with either unsaturated polyester (UPR) or a combination of UPR and vinyl ester, has been used on battery packs that have passed the stringent Chinese Standard GB/T 31467.3 test, commonly known as the “Chinese bonfire test.” FLAMEVEX, says IDI, offers designers a strong, lightweight and cost-effective alternative to steel and aluminum materials traditionally used to enclose battery packs in EVs and NEVs.
In August 2021, specialty chemicals company Lanxess (Cologne, Germany) and Korean auto parts specialist INFAC (Seoul), which specializes in automotive control cables, actuators, antennas and battery packs, announced a jointly developed battery enclosure. It uses Durethan BKV30FN04 from Lanxess to satisfy stringent mechanical and chemical property requirements. The halogen-free, flame-retardant and glass fiber-reinforced polyamide 6 (PA6) material is characterized by its optimized flame-retardant and electrical properties. Lanxess notes that the material is highly processable and enables the integration of complex functions required for housing components, resulting in a smaller number of parts and a simplified assembly process as well as lighter weight. The enclosure has been adopted to series production of EV models launched by a Korean OEM in 2021.
CSP’s multi-material battery enclosure demonstrator showcases the company’s ability to produce all components needed for a battery enclosure, including assembly, in a variety of materials per customer requirements. Photo Credit: CSP
Many composite battery enclosures typically use a metallic base on which the battery cells are mounted, with a composite cover over the top. In late 2020, Teijin Automotive Technologies (formerly Continental Structural Plastics, Auburn Hills, Mich., U.S.) and parent company Teijin Ltd. (Tokyo, Japan) announced development of full, multi-material battery enclosures that use composites in the lower tray and upper cover. “As one of the initial programs at our new Advanced Technologies Center [Auburn Hills], we designed and built the molding tools with production mold steel [P-20], and then we started formulating different materials and distinctive processes to enhance not just the molds but the parts themselves,” says Hugh Foran, executive director at Teijin Automotive Technologies. “We’ve been doing extensive testing. We have our own crash testing at GH Craft in Japan, so we’ve evaluated the different frames and have modified the box design somewhat, including adding some more ribbing to add more structure.”
Teijin has also worked with its suppliers on different preforms and fiberglass materials to add into the boxes, as well as battery suppliers to be able to test the full enclosure for thermal runaway requirements and evaluation under load. In addition to the battery, the enclosure itself comprises at least three structural components: a relatively thin composite top cover, a thicker and more structural composite bottom tray and a metallic ladder-shaped frame to provide additional support for the batteries within the box’s interior. Teijin has also developed an energy-absorbing structural foam interior frame that can be used for higher crash impact protection.
Also in late 2020, TRB Lightweight Structures (TRB, Huntingdon, U.K.) announced that it was establishing a new composite battery enclosure manufacturing operation in Richmond, Ky., U.S., for a customer producing electric buses. The highly automated fabrication line that TRB developed, in a joint venture with Toyota Tsusho America (New York, N.Y., U.S.), uses prepregged carbon fiber, automated cutting and compression molding to produce one enclosure every 11 minutes, and as many as 40,000 enclosures per year.
Carbon fiber wheels
The first carbon fiber wheels to be fully commercialized for the automotive industry were those produced by Carbon Revolution (Waurn Ponds, Australia), introduced to the market in 2008. In 2015, Carbon Revolution introduced carbon fiber wheels for the Ford Mustang Shelby GT350R. At $15,000 per set, however, these wheels were not a good fit for higher volume vehicles. Since then, a variety of automotive composites fabricators have been pursuing materials and process combinations that might allow carbon fiber wheels to compete — on cost and performance — with forged and cast aluminum wheels.
A 22-inch all-carbon fiber wheel for the Bentayga SUV. Photo Credit: Bucci Composites
That effort continued in 2021. In August, Bucci Composites SpA (Faenza, Italy) announced the development of a 22-inch all-carbon fiber wheel for British car manufacturer Bentley for its Bentayga SUV
Carbon fiber forged wheels showcased on the Vision Composite Products’ 5.0 Coyote Mustang. Photo Credit: IDI Composites International
In the fall of 2021, at the CAMX 2021 trade show in Dallas, Texas, U.S., Vision Wheel (Decatur, Ala., U.S.), a designer and manufacturer of off-road, racing and after-market automotive wheels, introduced its new carbon fiber wheel, developed in cooperation with IDI Composites International and composites braiding specialist A&P Technology (Cincinnati, Ohio, U.S.). The Vision Wheel carbon fiber wheel are fabricated with IDI’s Ultrium U660, a carbon fiber-based composite material. The spokes are fabricated using braided preforms supplied by A&P. The entire wheel is manufactured via compression molding. The price point of the wheel is not known, but Vision Wheel officials said that their goal was to be competitive with aluminum incumbents.
Higher volume, sustainability
Although a secular shift away from ICE powertrains and toward EV powertrains has begun, it will be more than a decade before production of ICE vehicles ceases altogether. In the meantime, automotive OEMs continue to look for ways to make vehicles more efficient. Composites find use in the automotive market — more than any other market served by composites — only by earning their way into programs and platforms. This means that composites must provide a highly compelling value proposition to motivate the carmaker to abandon traditional (and more familiar) materials and processes. This is the dynamic driving adoption of composites for battery enclosures, as described earlier in this article. A variety of announcements in 2021 signaled the applications that OEMs and the supply chain appear to see as promising for composite materials.
For example, in October, the UK government-funded research project TUCANA, AOC AG (Schaffhausen, Switzerland) and Astar (Biscay, Spain) announced the development of a new SMC based on Daron polyurethane hybrid technology that enables the production of chopped carbon fiber molded parts on an industrial scale with the mechanical performance of epoxy resin CF-SMC, and the manufacturing ease of UPR and vinyl ester resin SMC. Together, the CF-SMC supports the development of structural automotive parts with low density, E-coat capability and low emissions, while maintaining the design flexibility typical for composites. It will also be used in combination with Zoltek’s (St. Louis, Mo., U.S.) lower cost split-tow fiber.
The iPul pultrusion system developed by Pultrex, a KraussMaffei subsidiary, is able to produces large CFRP profiles in series. Tailored to Carbon TT’s requirements, it produces profile parts for around 70,000 vehicle chassis annually. Photo Credit: KraussMaffei
Also in October, Carbon Truck & Trailer GmbH (Carbon TT, Stade, Germany) announced the installation of an iPul pultrusion system for the manufacture of lightweight, CFRP profiles in series for high-load components for vehicles such as buses, small trucks and mobile homes. The new pultrusion system, delivered by Pultrex (a British KraussMaffei subsidiary, Lawford, U.K.) and tailored to Carbon TT’s requirements, produces profile parts for around 70,000 vehicle chassis annually.
GM’s 2019 model year (MY) Chevrolet Silverado pickups (top) sport a new structural application for composites in a hidden but very effective location: on the left and right front sides behind the steel bumper. The hybrid structural bumper bracket (below) was attached via a three-bolt/two-plane mechanical fastening system (see yellow outline) that reduces stress. Photo Credit: General Motors.
In July, CW reported on the design and development of a hybrid thermoplastic composite/metallic bumper bracket for the MY 2019 Chevrolet Silverado pickup truck. The mass of the pair of injection molded hybrid brackets was reduced 2.5 kilograms/vehicle versus the benchmark. And thanks to mass decompounding effects, lighter bumper corners enabled gauge reduction on the bumper mounting brace as well as other components, so total mass for the front bumper system was reduced 7.3 kilograms versus the outgoing 2016 model.
In April, CW reported on work being done by Advanced Composites Products & Technology Inc. (ACPT, Huntington Beach, Calif., U.S.) to develop new technologies to accelerate production of carbon fiber composite driveshafts for automotive use. The reason for increased driveshaft production is increased demand, caused, ACPT says, by carbon fiber driveshafts’ unique blend of capabilities compared to their metallic counterparts, such as higher torque capacity, higher rpm capability, better reliability, lighter weight, increased safety due to an inclination to break down into relatively harmless carbon fibers upon high impact and reduced noise, vibration and harshness (NVH). ACPT developed a two-spindle automated filament winding system with multiple winding carriages from Roth Composite Machinery (Steffenburg, Germany); and, rather than an immobile mounted automation system, a semi-automated mandrel handling system designed by Globe Machine Manufacturing Co. (Tacoma, Wash., U.S.).