The future of thermoplastics in the automotive industry
The use of thermoplastics in automotive manufacturing is not a new concept; manufacturers have made use of composites in several applications for many years. They have been used for non-load bearing parts and interiors such as battery frames and bumpers in mass produced cars, and for more complex applications such as the monocoque for high-end sports cars. However, until recently it has not been viable for thermoplastics to be used in mass production for cars and commercial vehicles for various reasons.
The time cycle, and therefore cost, of production of parts has been a particular stumbling block for manufacturers. There is a requirement to ensure that any composites used are of the necessary safety standards for today’s vehicles, along with the consideration of the environmental impact and recyclability of components due to End-of Life Vehicle (ELV) directives.
With car manufacturer’s constantly innovating design and looking for ways to make vehicles lighter and more efficient, the use of steel for the body and chassis of cars has been facing competition from other materials such as aluminium and fibre reinforced plastic (FRP) for some time. The development of carbon fibre reinforced plastic (CFRP) manufactured from thermoplastics, and the advancement of the process technologies to make parts, has given manufacturers the opportunity to use CFRP’s in many new applications and has made the possibility of mass production a very real prospect.
High performance composites
Thermoplastics were originally derived from structural polymer composites. (1) Epoxy and polyester thermosetting resins were reinforced with continuous filaments or fibres, and although structural polymer composites demonstrated several key benefits such as low density and good insulation, they were chemically unstable. Thermoplastics such as CFRP’s do not contend with the same issue as they utilise a thermoplastic matrix. They can be heated, re-molded and cooled several times without degradation, and are prone to less damage from production machinery due to their superior strength. Crucially for the automotive industry, they are recyclable; unlike thermoset composites.
CFRP materials possess an array of properties that make them attractive for manufacturing. (2) They are typified by high strength and rigidity; they have a low density, a greater dampening effect, and are highly resistant to impacting. They have excellent electrical and thermal conductivity and modifiable thermal expansion properties.
CFRP’s have been used extensively in aerospace engineering, the Boeing 787 being one such example (3), which uses composite materials in its airframe and primary structures. Almost half of the airframe is made up of CFRP and other composites, which provides a weight saving of around 20%. Formula One is another industry which has used CFRP for many years (4); in fact McLaren International first used a CFRP monocoque for their MP4/1C model in 1981 (pictured below).
The automotive industry as a whole aims to follow this lead of using CFRP more widely with the intention of weight saving and fuel economy at the forefront of design. Manufacturing processes are continually being developed, and will continue to be streamlined to make it possible to produce parts in a mass production scenario, both quickly and economically.