The Carbon-Fiber Future

Every year, auto shows arrive in cities around the world, but only a select few have the limelight and luster that is special to New York's. The auto industry has experienced tremendous changes in the past five years due to the roller-coaster ride of gas prices, the introduction of new technologies, and shifts in consumer taste. 

But one trend stands out: The lightweight composite materials on display at last year's New York International Auto Show offer insight into what to expect as the 2016 show opens later this month — and for the automobile models of the future. 

Feel the fiber

Carbon-fiber-reinforced polymer (CFRP) composites — also called carbon-fiber laminates — are the next-generation materials for making cars lighter, more fuel efficient and safer. Carbon laminate is extremely strong and stiff because of its woven layers of nearly pure carbon fibers bonded together by a hardened plastic, such as epoxy resin. Because the fibers are entirely carbon, their density is only about 1.6 grams per cubic centimeter (g/cc) — comparable to the density of table sugar — resulting in carbon laminates with densities of around 1.3 to 1.5 g/cc.

However, the carbon laminate manufacturing process is complex and requires either manual labor or expensive robotic machines, both of which result in high costs for the finished part. And, the most commonly used polymer (epoxy resin) requires 24 to 50 hours to solidify after it's infused into the carbon fiber, further increasing costs. In contrast, the density of steel is about 7.8 g/cc. Carbon fibers are slightly stiffer than steel, but have one-fifth the weight. Carbon laminate density is so low, it even beats the lightest structural metal, magnesium, which has a density of 1.8 g/cc. 

Making a statement

Predictably, high-end performance cars use large quantities of composites in their structures to reduce weight and reach the performance goals of higher top speeds, faster acceleration or increased battery life (in electric cars). 

However, the attractive appearance of carbon laminate, along with the public's fascination with this wonder material, has led to many cosmetic applications as well. In fact, the cosmetic applications are quickly making their way into high-volume-production automobiles.

An example of a car with an all-carbon body is the McLaren 570S — the structural panels and body frame are made of carbon laminates. This $185,000 supercar has a 562 horsepower V8 engine with twin turbochargers, giving it a 0-to-60-mph acceleration of 3 seconds and a top speed of 204 mph (328 km/h). Because so much of the car is made from composites, it weighs only 3,150 lbs. (1,429 kilograms).

Manufacturing a car like the 570S with an entirely composite structure is a massive undertaking. Since the first Formula 1 carbon-laminate car arrived in 1981, the technology has transitioned to only a select few production models — despite intense research and development efforts over the past 35 years. Some of the most complex challenges are producing carbon laminates in complex shapes, ensuring uniform penetration of the epoxy throughout the parts, taking into account the differing strength properties when the material is struck from different angles (strength is better in the direction of the fibers) and ensuring quality control. Overcoming these challenges is expensive, so carbon-laminate composites are only used extensively in models that are entirely performance-oriented, including the Alfa Romeo 4C, the new Ford GT and the hybrid Porsche 918. 

Carbon and electric

One significant avenue for the increased structural use of carbon laminates is electric cars. Lightweight materials are well suited to this emerging market segment because the driving range on one charge is extremely weight sensitive, battery placement options are improved by having complex form-fitting structural members and their appearance fits well with the futuristic aura that electric-car makers are trying to achieve. 

As electric cars continue to move from the top tier of the market, such as the BMW i8, to a more accessible segment — such as the Tesla Model 3, BMW i3 and Volkswagen  Golf — they will continue to rely on carbon laminates. The i8 and i3 already have carbon laminate bodies for reducing weight. 

The wide use as trim pieces underscores the popular desire to see advanced materials in even common cars. That car buyers associate carbon fiber with high performance and quality means the future for these materials in the automotive industry is promising. 

At the 2016 New York International Auto Show later this month, we anticipate seeing a wider adoption of existing carbon laminate parts, such as rearview mirror casings, spoilers and rear diffusers. These parts are made by specialized carbon-laminate manufacturers that can now customize them for other models at a lower cost. A more widespread use of some of the large-scale parts, such as seat structures, may also emerge this year. Extensive use of carbon laminates in a vehicle from a relatively more affordable segment, the BMW i3 — which achieved sales of 11,024 units in 2015 — will provide performance results in routine rugged driving conditions and better estimates for repair costs. Data from such models will help push carbon laminates into more mainstream cars. As the emissions standards tighten, all cars will require the lightening made possible by advanced materials. 

The new wave of electric cars will likely promote the merger of the functional and aesthetic roles of composites, and continuous improvement in carbon-fiber laminate technology is accelerating these applications. Already, engine cover, trunk liners and rear air diffusers appear to be on their way towards wider adoption. 

But perhaps most critically, the all-carbon-composite bodies of the i3 and i8 — and other production models — are providing data on the performance of hood and crash box designs in the event of a high-speed accident. So far, the outcome is excellent carbon composite performance under crash conditions, which will push usage further.