Thermoplastic Composite Leaf Spring is Ready for Series Production
An RTM process developed by Fraunhofer ICT allows parts to be produced using thermoplastic composites. It has been used successfully to produce an automotive leaf spring, demonstrating that it is ready to go into series production.
Scientists from the Fraunhofer ICT have produced automotive leaf springs made of thermoplastic composite fibres using a resin transfer moulding (RTM) process. Until now, thermosetting matrix systems have been used for the commercial production of composite fibre leaf springs. According to the scientists, it is much more economical to use the thermoplastic ε-Caprolactam in place of a thermosetting matrix system. Compared to epoxy resin, the raw materials costs for ε-Caprolactam are currently around 50% cheaper. The scientists use three to four kilograms of matrix to produce one leaf spring. What's more, the thermoplastic matrix makes the component completely recyclable.
The difficulty in processing thermoplastics in an RTM process arises due to exposure to moisture. That is why the anionic polymerisation of ε-Caprolactam to form polyamide 6 is highly sensitive to moisture. However, the working group at the Fraunhofer ICT has discovered a procedural solution to dealing with moisture. The scientists say that the process they have developed is now more resilient against external influences, meaning it is no longer necessary to pre-dry the semi-finished fibre products. For instance, this allows preforms that have not been dried out to be successfully processed during the production of the leaf springs.