Multiaxial fatigue of a short glass fibre reinforced polyamide 6.6 - fatigue and fracture behaviour

The multiaxial fatigue behaviour of a short glass fibre reinforced polyamide 6.6 (PA66-GF35) is investigated on hollow tubular specimens in the range of fatigue lives between 10(2) and 10(7) cycles. Fatigue experiments included pure tension, pure torsion, combined tension-torsion at different biaxiality ratios and phase shifting angles between the stress components. Tests were carried out with load ratio R = 0 and R = -1 at room temperature as well as at 130 degrees C. The influence of biaxiality ratio, phase angle between load components and load ratio is discussed. An extensive analysis of the fracture behaviour is performed on the specimens to recognise the crack nucleation and propagation mechanisms; failure modes were evaluated via optical and scanning electron microscopy.