Carbon fiber in automotive: At a dead end?

Photo Credit: BMW

For at least 40 years, the automotive market’s siren call has beckoned the attention of carbon fiber producers, with forecasts of large-scale adoption repeatedly unrealized. The first high-volume application I can recall was the filament-wound driveshaft for the 1984 Ford Econoline full-size van, at roughly 40,000 units per year. Within three years it was out of production, cost being a primary factor. Over the subsequent decades, carbon fiber shafts have made appearances on OEM platforms, but remained a relatively low-volume product. Similarly, in the early 2000s, excitement for carbon fiber grew as a slew of supercars and sports cars took advantage of an abundance of low-priced carbon fiber, but these applications did not translate into mainstream vehicles.

In 2013, with the introduction of the carbon fiber-intensive BMW (Munich, Germany) i3 and i8, and the creation of a dedicated supply chain to meet fiber and component demand, we waited (and waited) for other OEMs to follow suit, but none did. In 2015, we sang the praises of BMW’s “Carbon Core” multi-material philosophy on the mainstream 7-Series platform, seeing this as the breakthrough needed for triggering widespread proliferation of select components produced from carbon fiber. This concept has progressed within BMW on the forthcoming iX SUV (see “BMW rolls out multi-material Carbon Cage with with 2022 IX vehicle line”), but BMW is the exception, not the rule. Finally, at the 2017 JEC World exhibition in Paris, I noted at least a dozen B-pillar prototypes in all carbon fiber or carbon/steel hybrids, the “killer app” for carbon fiber in automobiles. Several producers have deployed the technology, but it has yet to really catch on globally. Ultimately, more effort is needed to get costs down so this application can win straight up versus an all-steel solution.

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At the CompositesWorld Carbon Fiber conference in Salt Lake City in November 2021, industry consultants Dan Pichler and Tony Roberts noted the imminent end of production of the BMW i3 platform, and with it, a significant drop in carbon fiber usage in the auto industry. They also emphasized there are no “announced” large-scale carbon fiber automotive projects in today’s pipeline, projecting only a 2.4% CAGR to 2026, mainly for motorsports, customization and low-volume niche platforms.

Wait. With the wholesale move from internal combustion engines (ICEs) to battery electric powertrains, won’t mass savings become more important, given the extra weight of the batteries? Doesn’t this portend great demand for carbon fiber? The answer to the first question is yes, reduction of vehicle mass is still very important. And to the second, carbon fiber is still a consideration, but only if it is cost effective. OEMs have several ways to reduce weight of automotive components, including replacing steel with aluminum.

Composites are of great interest for lightweight battery enclosures in battery electric vehicles (BEVs), as evidenced by the November Society of Plastics Engineers (SPE, Danbury, Conn., U.S.) Automotive Composites Conference and Exhibition (ACCE), where presentations on this topic, mostly focused on fiberglass enclosures, attracted the largest audiences. These enclosures are lighter than metal and can incorporate the thermal, flammability and EMI shielding functions needed at a competitive cost.

Alternatives to high volume fraction carbon fiber structures also continue to demonstrate favorable economics. More truck platforms are incorporating composite beds made from UV-resistant fiberglass sheet molding compound (SMC). An IACMI (Knoxville, Tenn., U.S.) project with Volkswagen of American (Herndon, Va., U.S.) demonstrated a glass fiber SMC SUV liftgate that is 36% lighter than steel with 9% lower recurring costs. Another IACMI project demonstrated that the addition of 10% chopped recycled carbon fiber to polypropylene can reduce injection molded part weight by 40% and part cost by 30% compared to a neat PA/PPE engineering thermoplastic. This points to opportunities not only for recycled carbon fiber, but also for fibers made from lower cost precursors like textile PAN and coal tar pitch.

Is the use of traditional carbon fiber in automotive at a dead end? Not entirely, but don’t expect carbon fiber-intensive vehicles like the i3 to return in mass production. There is a narrow path to achieve carbon fiber structure with 50% fiber volume at a finished cost of $10/pound ($22/kilogram), and it will require improvements all along the manufacturing chain. This will open discrete opportunities in individual components like B-pillars. In the nearer term, we can expect to see carbon fiber shapes, perhaps pultruded, used as stiffening elements in hybrid overmolded structures (including structural battery enclosures) where glass fiber-reinforced polymers make up the balance.

Composites have a great future in the automotive market, led by fiberglass, augmented by niche applications of traditional carbon fiber. For suppliers of recycled carbon fiber and fibers made via alternate precursors, the opportunity space is considerably brighter.