Considering anisotropic behaviour and process-induced weaknesses in fibre reinforced polymers in CAE

Abstract

Computer Aided Engineering (CAE) is widely used for developing new products nowadays. Through advanced software, it is possible to simulate the reality in the computer to save time and money when less component testing is needed. Two examples of CAE are Finite Element Analysis (FEA) and Mould Fill Simulation (MFS). MFS can be used to simulates the melt flow in the mould of an injection moulding process and FEA can be used to structurally analyse components when subjected to various loads. This thesis work was conducted at Thule to investigate the possibility of consider the anisotropic behaviour and process induced weaknesses of short fiber reinforced polymers (SFRP) through MFS in Moldex3D with a subsequent FEA in LS-DYNA. The MFS results was implemented in the FEA through the usage of material models Mat_157 and Mat_215 which are designed for fibre reinforced materials. A tensile test using Polyamide 6 reinforced with 30 wt% short glass fibres (PA6 GF30) specimens was performed and compared with results from the corresponding MFS and FEA. A subsequent Case Study on Thule’s Outway Hanging Bike Rack was performed, which also included physical testing, MFS and FEA. Results indicate that it is possible to capture the anisotropic behaviour of SFRP by obtaining the fibre orientation through MFS. Also, some process induced weaknesses, especially weld lines and air traps can be obtained from MFS. In the FEA, the comparison of material models shows that the implementation of fibre orientation can increase the reliability of the analysis, but there is a need for material testing with combined calibration of the material models before they can be implemented in the daily calculations at Thule.