Numerical Methodology Development and Validation for Fatigue Life Prediction of PA-6 Long Fibre Thermoplastic Material Manufactured Using Compression Moulding

This paper presents a numerical methodology developed for the modelling of fatigue life of PA6 long fibre thermoplastic (LFT) material with 40% glass fibre content (PA6-LFT40) produced using compression moulding for the incorporation of long fibre, which enhances the mechanical properties compared to injection-moulding. Firstly, compression moulding process simulations were performed to predict fibre orientation using Autodesk Moldflow. Model parameters for process simulation were calibrated until the predicted fibre orientation matched the orientations obtained using micro X ray-Computer Tomography on PA6-LFT40 plates. The calibrated fibre orientations were then mapped to a finite element method (FEM) solver mesh to perform standard static three point bending test. Tensile tests served as the corresponding material model inputs for the simulations. Using mapped FEM simulation, the deviation between simulation and tests were less than 10% that is much better than without mapping. Finally, using the experimentally determined Haigh diagram, three point bending fatigue testing of PA6-LFT40 at different load levels at a stress ratio of R = -1 were performed and evaluated by using FEMFAT. The predicted fatigue life at different load level showed good correlation with test results. In conclusion, the developed numerical methodology, enhances the predictive modelling of fatigue life of compression moulded LFT Composites.