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BMW iX

As the automotive industry focuses on electrification, new opportunities exist for composites to lightweight vehicle components and protect the newer, larger batteries on battery-electric vehicles (BEV). Shown here, the BMW iX BEV features a multi-material composites-intensive frame.
Photo Credit: BMW

Low-volume, high-end vehicles and motorsports have made frequent use of composite materials for years, favoring continuous carbon fiber materials for high-performance, lightweight vehicles.

The more cost-sensitive market for mid- and high-volume production vehicles has been slower to adopt composites. However, a steady, incremental increase has been seen in the use of continuous glass fiber-reinforced polymers (GFRP) in applications such as leaf springs, as well as sheet molding compound (SMC) for applications like body panels and frames, bulk molding compound (BMC) for housings and support structures and injection molded thermoplastics for bumper frames, lift gates and seat structures.

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More recently, new opportunities for composites use on commercial mid- and high-volume vehicles have come about as the automotive industry ramps up production of battery-electric vehicles (BEV). According to the U.S. Department of Energy (DOE), sale of plug-in vehicles — including BEVs and hybrid electric vehicles — rose nearly double in 2021 compared to 2020. Batteries in BEV are heavier than internal combustion engine (ICE) vehicle batteries, necessitating lightweighting elsewhere in the vehicle to maximize the vehicle’s range and efficiency.

 

Battery enclosures

Teijin Automotive composite battery enclosure

Tier suppliers (like Teijin Automotive Technologies, whose SMC battery enclosure is shown here) continue to work with OEMs to produce new designs and processes to produce battery enclosures meeting various vehicle needs. Photo Credit: Teijin Automotive Technologies

Electric vehicle (EV) battery enclosures — covers and trays that hold and protect the frames and battery cells within an EV — are perhaps the area with the most opportunity for composites in automotive right now, led by the need for OEMs to reduce the mass of the overall battery pack. As reported by CW in Part 1 of a two-part 2022 feature on composite enclosures, empty metallic battery enclosures are said to add 110-160 kilograms to vehicle mass even before they’re loaded, making them the heaviest component on BEVs — presenting an opportunity for lighter weight composite materials.

Beyond lightweighting, switching to composite battery enclosures can also enable a host of other benefits such as more complex geometries, better impact performance, corrosion resistance, faster assembly, greater durability and — with specific formulations — better flame resistance/fire containment.

Aiming to support the needs of this growing market, innovative solutions are under development at each level: materials development and testing, design software, parts design and new processes.

Materials. As reported by CW in Part 2 of 2022’s battery enclosure feature, materials suppliers have made substantial efforts to develop higher performing composites that meet current and future needs of automakers and battery module producers as performance and safety requirements become more demanding. Among these innovators are INEOS Composites US LLC (Dublin, Ohio, U.S.), Johns Manville (JM, Denver, Colo., U.S.), Lanxess AG (Köln, Germany), LyondellBasell Industries (Houston, Texas, U.S.), Mitsubishi Chemical Group Corp. (MCG, Tokyo, Japan), SABIC (Riyadh, Saudi Arabia), Solvay SA (Brussels, Belgium) and Westlake Chemical Corp. (Houston, Texas, U.S.).

material testing for composite automotive battery enclosures

Materials suppliers have to meet increasingly stringent requirements for battery enclosures. Shown here is a material sample undergoing a test for UL’s 2596 thermal runaway standard. Photo Credit: UL, via Forward Engineering GmbH

One driving factor for materials development is more stringent requirements and testing standards for battery enclosures. An example is UL’s (Northbrook, Ill., U.S.) standard 2596, which was made available in January 2022, co-developed with Forward Engineering North America LLC (Royal Oak, Mich., U.S.) and Hyundai-Kia America Technical Center (HATCI, Superior Township, Mich., U.S.). Named the Battery Enclosure Thermal Runaway (BETR) evaluation, UL 2596 is a process for reliably evaluating thermal runaway in battery enclosure material samples. A follow-up Torch and Grit test (TaG), announced by UL in October 2022, is expected to be published as an addition to 2596 in 2023.

Part design. At the parts level, a number of creative battery enclosure designs have also been announced to the market, aiming to cover a wide range of OEM needs — two reported by CW in 2022 include HRC Group’s (Changshu, China) one-piece SMC module developed for high-volume, low-cost production; and Katcon’s (Monterrey, Mexico) multi-material toolbox of options.

Processes. Supporting these designs are new processing methods aiming at low-cost, high-rate manufacture of these parts, from SMC solutions to resin transfer molding (RTM) and wet compression molding (WCM, also called liquid compression molding, LCM). One example CW has reported about is CpK Interior Products Inc.’s (Corbyville, Ontario, Canada) UniFORM process, which adds specialized tooling and vacuum assistance to WCM in an effort to reduce cycle times and manufacturing costs while achieving high part performance.

 

Structural components, leaf springs and more

Battery enclosures for EVs tended to dominate automotive composites headlines in 2022, but ICE vehicles are far from out of the picture. For both EVs and ICE vehicles, OEMs continue to incrementally adopt composite structural components in vehicles where they make sense, and to move toward more efficient, more automated processes for increased volumes.

For example, in 2022 BMW Group (Munich, Germany) rolled out its newest battery-electric sports activity vehicle (SAV), the iX, featuring a “Carbon Cage” body frame that combines RTM’d braided preforming, fiber-reinforced thermoplastic injection molding, compression molding and metallics in a multi-material design that builds upon BMW’s previous composite strategies for the i3, i8 and 7-Series.

BMW iX carbon cage assembly

The 2022 BMW iX battery-electric sports activity vehicle (SAV) features a multi-material combination of metals and composites in its innovative Carbon Cage. Illustrated by Susan Kraus

Rassini hybrid leaf spring installed on Ford F-150 truck

Rassini’s 1+C hybrid leaf spring features a single steel parabolic main plate and a flat glass fiber composite helper plate to provide suspension on the rear wheels of the Ford F-150 pickup truck. Photo Credit: Rassini

Composite leaf springs and leaf spring components also continue to be a leading market for composites in automotive. For example, the Grand Award winner of the 2022 SPE Automotive Innovation Awards is an all-composite leaf spring for light truck programs, developed by Mubea (Attendorn, Germany) for General Motors Co. (Detroit, Mich., U.S.). The leaf spring, manufactured with fiberglass-reinforced epoxy prepreg, is said to reduce mass up to 75% compared to an all-steel leaf spring, and 58% compared to hybrid steel/composite leaf springs.

Another recent innovation in this field, winner of a 2021 Altair Enlighten Award, is Rassini International’s (Plymouth, Mich., U.S.) multi-material steel/composite leaf springs. The product of a project with Ford Motor Co. to take weight out of the rear suspension of the F-150 pickup, Rassini’s solution integrates traditional steel leaf springs with a composite “helper” manufactured via a highly automated high-pressure resin transfer molding (HP-RTM) process.

In addition, demonstrators and R&D continue to test the limits of automotive parts processing, including the use of 3D printing and automated fiber placement (AFP), recently demonstrated by the Technical University of Munich (TU Munich, Germany) and BMW to produce a mid-chassis roof frame. An extension of the work that led to some of the innovation on the BMW iX, this project combined an extrusion-based, 3D-printed core with AFP skins to produce a roof frame with comparable strength and stiffness to a hollow steel part, but that is 40% lighter and avoids the cost of injection molding tools.

 

Carbon fiber wheels

Carbon fiber wheels also continue to gain traction. 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.

carbon revolution carbon fiber wheel

Render of a Carbon Revolution 26-inch one-piece carbon fiber wheel. Photo Credit: Carbon Revolution

These efforts continued in 2022, with particular focus on the aftermarket segment. For example, Carbon Revolution, in addition to its premium wheels, announced the development of 23- and 24-inch carbon fiber wheels targeted for aftermarket sales into the EV truck and SUV market. Notably, the company has also begun demonstrating its wheels’ capabilities for the aerospace market, recently working on a concept and validation project for a Boeing (Chicago, Ill., U.S.) CH-47 Chinook helicopter wheel.

In August 2021, 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. Said to be the largest all-carbon fiber wheel ever made, it is fabricated via high-pressure RTM (HP-RTM) and offers weight savings of 6 kilograms per wheel. Bucci Composites says the lighter wheel results in less rotational inertia, which translates into greater acceleration, shorter braking distance and better vehicle handling. In October 2022, Bucci presented its first 20-inch carbon fiber rim dedicated to the aftermarket, especially for the sport/supercar sectors.

carbon fiber composite Vision WHeel

After several years of development and testing, Vision Wheel’s current design combines SMC reinforced with continuous braided fiber in the spokes. Photo Credit: IDI Composites

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 aftermarket automotive wheels, introduced its new carbon fiber wheel, developed in cooperation with IDI Composites International (Noblesville, Ind., U.S.) 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. At launch, the costs were reported to be $2,000 or less per wheel.

Also in 2022, ESE Carbon Co. (ESE, Miami, Fla., U.S.) launched its E2 one-piece carbon fiber composite wheels into the market for the aftermarket segment. The initial E2 launch included 19- x 8.5-inch wheels, servicing Tesla Model S, Tesla Model 3 and Subaru WRX STI vehicles. In development since the company was founded in 2011, ESE’s wheels are manufactured via tailored fiber placement (TFP) and HP-RTM to produce a lightweight, single-piece, high-performance wheel.

 

Focus on sustainability

natural fiber BMW

The latest M4 GT4 race car model with several natural fiber components. Photo Credit: BMW, Bcomp

Beyond a focus on electrification, the automotive industry also continues to innovate toward more sustainable material solutions for many components, from natural fiber composites to bio-based resins, recyclability and more.

Here are a few examples of developments in this area reported in 2022:

Landscape Photo Credit: Katcon

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