FATIGUE LIFE ASSESSMENT OF INJECTION-MOLDED REINFORCED SHORT FIBRE THERMOPLASTICS: NOTCH EFFECTS

摘要

The automotive industry needs to reduce the weight of vehicles for environmental and economical purposes. One expected way to reach this goal is to use reinforced thermoplastics for the design of mechanical structures because of their high ratio "fatigue strength/density" compared with metallic materials. During its life, each automotive component can be submitted to repeated loadings with variable amplitude. As in service failures must be avoided, fatigue characterization is necessary to optimize the design of thermoplastic parts. A specific methodology for multiaxial fatigue life assessment of injection-molded components was previously proposed to this aim [1]. The latter, called 'Through Process Modelling' (TPM), allows linking the injection process simulation to the fatigue life assessment with a fatigue criterion, through the estimate of heterogeneous local anisotropic properties due to variable fibre orientation. One of the major advantages of such an approach is to account for microstructure orientation influence, due to injection process, on fatigue life. The relevance of the TPM has been discussed by using as a reference a large multiaxial fatigue database for PBT-PET GF30 and PA66 GF35 involving in each case different type of injectionmolded samples and various fatigue loadings (tension, torsion, combined tension-torsion, pure shear with two load ratios). Very good results were obtained for both materials with an energetic fatigue criterion using only one S-N line for the identification.