Composite materials are finding their way in automotive design

When BMW launched its i3 electric hatchback in 2013, it was considered a test bed for new technologies that were expected to play important roles in the future of electric automobiles. One of these was carbon fiber, which BMW used for the i3’s body panels and some of its structural parts. At that time, many expected that carbon fiber composites, which can be as strong as metal and far lighter, would soon become the material of choice for EV body panels.

The i3 is still around—indeed, it has become something of an elder statesman in the EV world.  However, the projected takeover of carbon fiber has not taken place. Tesla’s three-step master plan provides an example of the progression—or, as some might say, regression—of EV-makers’ materials choices. The Roadster used carbon fiber body panels, Models S and X use aluminum, and the latest generation—Models 3 and Y—uses a combination of aluminum and steel. Ford used mostly steel for the body of its Mustang Mach-E, and predominantly aluminum for its F-150 Lightning.

There are surely several reasons for these choices, but the one that’s most often mentioned is price. EV designers have apparently decided that the lower weight of carbon fiber and its other advantages do not justify the price premium.

So, is carbon fiber destined for the trash can of automotive history? Far from it. Automakers haven’t given up yet on using composite materials as parts of the body-in-white and other structural elements, such as leaf springs. And there are certain EV-specific applications for which composites offer a compelling alternative.

One of these applications is the battery housing, which demands strong flame retardancy and crash resistance properties. Another one is the rotor sleeve—a lightweight sleeve that reinforces the motor and protects it from road debris. This application requires a tough material that won’t interfere with the magnetic field of the motor—and lighter weight is always welcome.  

Pressure vessels represent a third common application for composite materials. These have been found in automobiles for years, used to store LNG, and may eventually see a rising demand to store hydrogen. This is an ideal and well-established application for composite materials.

Every automotive designer knows that choosing the right material for the right part is a critical and complex process—and this is certainly true when it comes to composites. Materials suppliers offer a range of resin systems for composites, and leading firms work closely with their customers to choose the right formulation with the most appropriate properties for each part and each manufacturing process.

The conversation on the desired parameters for a specific application will soon pass out of the realm of comprehension of the layman, or indeed of anyone other than an automotive manufacturing expert.  Topics such as battery protection standards, flame retardancy ratings, glass transition temperatures and viscosity are the domain of the engineer—but they are critical.

Automotive composite suppliers must develop very close relationships between their materials experts and their customers’ manufacturing process designers. Huntsman Advanced Materials, which supplies a wide range of ARALDITE® epoxy-based resin systems, as well as adhesives and encapsulants, prides itself on its long history of working closely with customers to select the right materials and manufacturing processes for mass production of each particular component.