Micro-mechanisms of fatigue in short glass fiber reinforced polyamide 66: A multi-scale experimental analysis

Abstract

The objective of this work is to identify and to analyze the main micro-mechanisms which govern the fatigue behavior of a short glass fiber reinforced polyamide 66 composite through a multi-scale experimental analysis. Tension-tension fatigue tests have been performed at different applied maximum stress and have been analyzed at both microscopic and macroscopic scale. Together with the progressive stiffness reduction, the temperature rise due to self-heating during cyclic loading has been measured using an infrared camera. Moreover, SEM fractography observations have been performed to assess the chronology of deformation mechanisms. Two principal mechanisms have been identified: matrix deformation due to self-heating and fiber-matrix interface damage. In addition, localized deformation zones have been observed around the fibers. The evolution of the size of these micro-ductile areas have been statistically related to the maximum applied stress. Finally, a competition between thermal fatigue and mechanical fatigue have been shown according to the loading amplitude.