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Toyota using Mitsubishi Rayon’s carbon fiber SMC for hatch door frame of new Prius PHV

Mitsubishi Rayon (MRC) (which is now consolidated into Mitsubishi Chemical, along with Mitsubishi Plastis and the former Mitsubishi Chemical) recently announced that its carbon fiber sheet molding compound (SMC) has been adopted for the rear hatch frame of the new Toyota Prius PHV. SMC is a form of thermoset chopped fiber composite; glass fiber reinforced SMC is already commonly in use in the automotive industry.

SMC developed by MRC is a type of intermediate material for CFRPs and a sheet-shaped material in which carbon fibers cut into several-centimeter lengths are dispersed in resin. The SMC can be processed into components in a short period of time—roughly 2 to 5 minutes—by press molding. In contrast to prepreg intermediate materials (uncut carbon fiber fabric impregnated with resin), this SMC features high formability for molding complicated shaped parts.

It also exhibits close-to-uniform mechanical properties. This allows engineers to readily use the carbon fiber material by utilizing existing parts design know-how and achieve lighter components with higher strength.


Advantages of MRC’s SMC for the Prius PHV include a substantial reduction in the vehicle’s weight, the achievement of a great component performance, an excellent formability that enables production of complicatedly shaped components, and productivity necessary for manufacture of components for mass-produced vehicles.

Lux Research called MRC’s contract win small, but important. Lux said that three key lessons can be gleaned from the announcement:

  1. Use case matters. The CF SMC is still substantially more expensive than aluminum or glass fiber SMC. On a pure fuel efficiency vs cost basis, its adoption not likely justified. However, the PHV model will benefit substantially more than the base model, due to the increase in full-electric range from lightweighting.

  2. SMC is much simpler to design with than continuous fiber composites. SMC has uniform properties—unlike continuous fiber composites—making it much more like metals for design engineers and much easier to adopt over all.

  3. Fast speed is not as necessary for initial adoption. The product takes two minutes to five minutes to mold. Most automakers have said that one-minute cycle times are necessary for mainstream adoption, but it’s clear from this announcement that niches exist where longer cycle times are acceptable, Lux observed.

Bolstered by the Toyota win, MRC said it actively and extensively promote the use of its carbon fiber materials for automotive components. Mitsubishi Chemical Holdings Group’s APTSIS 20 Medium-Term Management Plan aims for achieving sales of ¥100 billion (US$900 million) from the carbon fiber and composite material business in 2020.

Earlier this year, MRC acquired a US carbon fiber plant from SGL—SGL Carbon Fibers LLC, in Evanston, Wyoming—to expand its carbon fiber business in the North American market. MRC also acquired Seattle-based Gemini Composites LLC, a design, engineering and prototyping firm specialized in product development using forged composite technology.


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