Manufacturing of a thermoplastic door surround structure

Abstract

Thermoforming of thermoplastic composite structures can produce high quality parts with extensive throughput. However, high performance thermoplastic matrices often suffer from large warping due to the increased temperature required by the process and the crystallisation of the matrix. Complex geometries can also cause folds and ripples in the fibres which reduce performance. Those imperfections have to be countered by changes to the preform holder and by cuts in the preform. A detailed simulation process chain respecting crystallisation and thermal shrinkage during the cooldown is necessary to compensate spring-in. The simulation process chain has tobe supported and validated by experiments. Folds in the laminate can be examined by detailed forming simulationsif sufficient material and process data can be provided. At the German Aerospace Center in Stuttgart the process chain was applied to a generic segment of a door surround structure. Using a detailed material model for carbon fibre reinforced low-melt polyaryletherketon (CF/LM-PAEK), the warping during the cooldown was simulated and used to modify the tooling. A forming simulation afterwards showed thickness changes due to shearing and folding of the preform. Different strategies were tested to minimise these effects. The whole process chain was verified with multiple manufactured parts using the modified process.