On the thermo-visco-elastic behaviour of neat and aged PPS composites

Reinforced PPS thermoplastics exposed to variations in temperature and humidity are subject to aging and interface degradation. These phenomena can lead to ruptures due to the interphase weakening. In this study, a micromechanical model based on the equivalent inclusion model is implemented using the viscoelastic behaviours of the neat and aged grades identified by spectrometric analyses. The presented coated inclusion model allows to extract the viscoelastic behavior of the interphase in the dry-as-molded composite and in the aged composite by inverse method conducted for viscoelastic behavior. The presence of the interphase testifies to the degradation of the thermomechanical properties in the vicinity of the reinforcements. In the aged composite, the interphase also undergoes an aging phenomenon. Thus, the model compares the behavior of the interphase in the dry-as-molded and aged grades of the composite and separates the effects linked to the degradation of adhesion of the fibers from the effects linked to specific hydroscopic aging.