A UK consortium has demonstrated that lightweight automotive components can be produced economically and with minimum impact on the environment.
Exterior and interior automotive components have been produced from self-reinforced polymers, which offer improved weight reduction, recyclability, impact performance and surface finish compared to glass-reinforced composites.
The prototype components have been developed as part of a 2 year research and development project, called RECYCLE, supported by the EPSRC and DTI, under the LINK Foresight Vehicle Programme, administered by the Society of Motor Manufacturers and Traders (SMMT).
The RECYCLE project investigated the processing, joining and finishing technologies required to produce automotive parts from self-reinforced polypropylene and evaluated their recyclability and sustainability. The project was led by NetComposites, a composite materials research, consultancy and online media company based in Chesterfield, UK, and included Lotus Engineering, BI Composites, Propex Fabrics, the University of Warwick, Trauma-Lite and London Taxis International.
Polypropylene is a popular material in the automotive industry due to its low cost and good all round properties. However, for many applications polypropylene has insufficient stiffness and needs to be reinforced, with glass fibres for example, although this reduces recyclability and can make it difficult to achieve an acceptable surface finish. Instead, by reinforcing polypropylene with fibres of the same polymer, a material can be produced that has intermediate stiffness, exceptional impact performance, a ‘class A’ surface finish and is fully recyclable.
One such material, produced by Propex Fabrics under the trade-name Curv (http://www.curvonline.com), is currently being considered for components such as under-body shields but with other potential applications including cosmetic panels and pedestrian and occupant protection.
The consortium initially developed processing techniques whereby the self-reinforced polypropylene sheet was successfully formed into shapes with various complexities. Suitable techniques for joining and finishing were identified and tested to standard automotive specifications, and the ability to produce recyclable all-polypropylene sandwich structures was also demonstrated by combining self-reinforced polypropylene skins with lightweight core materials, including expanded polypropylene foam and polypropylene honeycomb. Recycling routes were identified for post-manufacture, post-processing and post-consumer waste streams.
The results were then applied to the design and manufacture of the 2 prototype components, a Lotus Elise front access panel and a generic interior panel. The self-reinforced polypropylene front access panel was found to be 57% lighter than the current production part and passed mechanical and paint durability tests. Sustainability analysis indicated that the total cost of the self-reinforced polypropylene part was also slightly less than the current production part, primarily due to the shorter cycle time and subsequent labour savings. Generic interior panels were produced with a variety of finishes, including textured TPO, metallic foils and fabrics. Life cycle analysis highlighted significant benefits to the environment in terms of reduced energy consumption and toxicity compared to competing materials.
Gordon Bishop, Managing Director of NetComposites, said “self-reinforced polymers have huge potential in the automotive sector by reducing weight and environmental impact, at the same time as offering a unique property profile, but so far their application has been limited. In this project we have developed the technology and know-how to be able to apply these materials in many more applications in the vehicle sector, in both interior and exterior applications, and we are now in the stages of applying the benefits of self-reinforced plastics in a number of vehicles.”
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