Fatigue mechanisms description in short glass fibre reinforced thermoplastic by microtomographic observations

Short glass fibre reinforced thermoplastics are promising materials for weight reduction of structures thanks to its very good specific mechanical properties. The current challenge is to provide experimental data concerning damage mechanisms and their kinetics in order to enhance micromechanical models for these materials with complex behaviour. The objective of this work is therefore to observe and explain damage mechanisms regarding spatial configuration of the microstructure. Fatigue tests have been running on reinforced polyamide specimens and interrupted at different levels of the estimated life. 3D pictures of the gage length of these specimens have been obtained by microtomography with high resolution (0.65 µm). This data presents damage location at different stages of lifetime. Thus, debonding, matrix damage and fibre failure have been identified as the three damage mechanisms for these materials. The analysis of the evolution of the damage markers quantity, volume and aspect ratio inform about the kinetic for each mechanism during the material life.