Thermomechanical behavior of PA6.6 composites subjected to low cycle fatigue

In this study, manifold experiments were conducted to investigate the thermomechanical behavior of short E-glass fiber-reinforced polyamide 6.6 composites subjected to low cycle fatigue loadings. Different hygrometric states, fiber configurations and loading rates were considered. Mechanical, thermal and energy responses of composite specimens were recorded using photomechanic techniques. The influence of water content, fiber orientation and loading rate on these thermomechanical responses was systematically analysed. The mechanical findings indicated that the ratcheting phenomenon was more pronounced for humid composites reinforced with fibers oriented transversely and subjected to a low loading rate. Moreover, the order of magnitude in self-heating was greater for transversal fiber composites conditioned at high relative humidity and subjected to a 10 Hz loading rate. From a thermodynamic standpoint, we also noticed that high proportions of the mean stored energy rate were obtained at a high loading rate, with values exceeded 64%. These values were noticeably altered by the water content and fiber angles, i.e. lower as the relative humidity increased and higher as the fiber angles increased. (C) 2015 Elsevier Ltd. All rights reserved.