Prediction and Validation of Anisotropic Elastic Property of Injection Molded PA66/Carbon Fiber Composites Parts for Automotive Applications

Abstract

Automotive parts made with injection molding of carbon fiber reinforced polymers (CFRP) have shown significant advantages in lightweight vehicle development. Featured with balance between performance and cost, injection molded CFRP components are suitable for various automotive components. However, most concurrent computer aided engineering (CAE) analysis of such components still adopts homogeneous and isotropic cards for composites materials. Often is the case that high safety factor have to be used during design practice for composites parts due to incapability of accounting for anisotropic material behavior, which limits the application of the CFRP materials. While numerous studies have demonstrated the prediction of anisotropic material properties for fiber reinforced polymers through fiber orientation prediction and micromechanics calculation, validation is rarely done on an actual automobile part with complex geometry, which constrains the confidence of design engineers to perform analysis with anisotropic material properties for CFRP parts. In order to bridge such gap, in the present study, a vehicle part is manufactured using PA66/carbon fiber composites through injection molding process. Tensile tests are performed on samples cut from different locations of the part. Injection molding simulation based on actual processing parameters is performed to provide the fiber orientation predictions. The anisotropic elastic properties throughout the parts are obtained through the combined usage of micromechanics and orientation tensor averaging procedures to provide the anisotropic elastic properties in the parts, which are varying from element to element. A mapping process is also developed to transfer properties between the different meshes used in processing simulation and structural finite element analysis (FEA). To compare with the experimental results and validate the prediction of anisotropic elastic properties, the part model in FEA is virtually cut at the same locations as the real experiment samples to provide tensile bar FEA models, which enables FEA simulated tensile tests. Good match is observed between the experiments and FEA simulations at coupon level tests, indicating the accuracy of predicted anisotropic elastic properties from prediction.