The assessment of fatigue damage on short-fiber-glass reinforced polyamides (PA) through the surface roughness evolution

This paper analyses quantitatively the surface damage generated by the fatigue micromechanisms of the polyamide 6.6 (PA 6.6) reinforced with short fibre glass, with a series of specific tests for determining the surface roughness (RA) of the normalised specimens previously fatigue tested. The study has demonstrated that when the viscoelastic material is deformed in the fatigue process at a constant speed (d2ε/dN2 = 0), crazing phenomena start to appear, distributed uniformly throughout its core. The effects of this damage, which is permanent and can be detected using sweep electron microscopy techniques (SEM), have been quantified through the measurement of the surface roughness of the specimens. In this way, the evolution of the roughness of the material is established as a qualitative index of the development of the nucleation of crazes and, thus, of irreversible damage, as these emerge towards the surface of the material