Researchers develop technique to mass produce thermoplastic fibre components
Researchers claim to have found a way for the automotive industry to mass produce a particularly safe class of materials known as thermoplastic fibre composite components. A team from the Fraunhofer Institute for Chemical Technology ICT in Pfinztal say that once the materials have reached the end of their useful life, they can be shredded, melted down and reused to produce high quality parts.
The researchers add that the materials perform 'significantly' better in crash tests as thermoplastic components, reinforced with textile structures, absorb enormous forces generated in a collision through viscoelastic deformation of the matrix material without splintering.
Previously, it had not been possible to come up with a suitable manufacturing technique for thermoplastic composite structures made from high performance fibres, but the ICT engineers say they have now developed a process which makes it possible to manufacture up to 100,000 parts a year.
Dieter Gittel, a project manager at ICT, said: "Our method offers comparatively short production times. The cycle time to produce thermoplastic components is only around five minutes. Comparable thermoset components frequently require more than 20 minutes."
The Fraunhofer researchers have named their technique thermoplastic RTM (T-RTM). It is derived from the conventional RTM (resin transfer molding) technique for thermoset fibre composites. The composite is formed in a single step. Gittel explained: "We insert the preheated textile structure into a temperature controlled molding tool so that the fibre structures are placed in alignment with the anticipated stress. That enables us to produce very lightweight components."
The preferred types of reinforcement comprise carbon or glass fibre and the researchers claim to have also developed specialised structures. The next step involves injecting the activated monomer melt into the molding chamber. This contains a catalyst and activator system – chemical substances that are required for polymerisation. The researchers can select the system and the processing temperature in a way that enables them to set the minimum required processing time.
The team says that a demonstration part has confirmed the benefits of this new class of material. According to the researchers, the trunk liner for the Porsche Carrera 4 weighs up to 50% less than the original aluminium part. To improve the crash behaviour of the vehicle's overall structure, the ICT engineers also calculated the optimum fibre placement. The cost of the thermoplastic matrix material and the cost of its processing are said to be up to 50% lower than the equivalent costs for thermoset structures.
Over the next few years the researchers believe that these kinds of components will start to be used in vehicle and machine construction as well as in the leisure industry.
