Teijin Ltd announced March 9, 2011, that it has developed a technology to press thermoplastic CFRP (carbon fiber reinforced plastic) into shapes within one minute.
The company expects that the technology will be used for making parts of mass-produced cars, which require short takt times, by combining it with an injection molding technology for thermoplastic CFRP and a technology to join thermoplastic CFRP components together.
In fact, Teijin made a concept car by attaching a motor, suspension, tires etc to a prototyped car body frame (white body) whose size is equivalent to that of a kei car and mass is 47kg. The concept car can be actually driven.
As resin components, various thermoplastic resins including polypropylene (PP) and polyamide (PA) can be used. The prototyped white body uses both PP and PA components that were formed by press molding and injection molding. The number of the components is more than 20.
In press molding, an in-process material is formed by impregnating a carbon fiber with a thermoplastic resin. Teijin uses two types of the in-process material, which are (1) a unidirectional base material suited for components that require high strength in a limited direction and (2) an isotropic base material that has the same strength in any direction and high freedom degrees in terms of shape and material design.
Every component used for the prototyped white body was formed in a single press process, the company said.
In injection molding, a pellet containing long fibers (LFT: Long Thermoplastic pellet) is used as an in-process material. Though its strength is slightly lower than that of a press-molded component, the LFT is suited for making components with complicated shapes such as those used for joints. It is possible to use existing injection molding machines for shape forming.
For joining CFRP components together, Teijin used some metallic rivets for the prototype. But it uses a newly-developed joining technology, instead, to realize a takt time of one minute or less. Though the company has not disclosed the details of the technology, it said, "it is more like welding than adhesive bonding." Teijin also utilizes a technology to join components made of different materials like CFRP and metal.
Thermoplastic CFRP not only reduces takt time but also improves recycling efficiency. And the technology to form CFRP parts in a short time probably can be applied to not only the components of cars but the components of machine tools and robots.