Mechanical response of a unidirectional graphite fiber/polyimide composite as a function of temperature

In this work, the mechanical response of a unidirectional composite based on T650-35 graphite fibers embedded in a PMR-15 polyimide resin was analytically and numerically predicted as a function of temperature and subsequently compared with the available experimental data. The Eshelby/Mori–Tanaka (E/M–T) method was used to predict the elastic properties of the composite, whereas a finite element unit cell was employed to predict the stress vs. strain curves of the composite under elasto-plastic conditions. It was shown that for the temperature range from 25 to 315 °C the predicted elastic properties of the composite agreed closer with the experiment in the case of the longitudinal and transverse Young’s moduli than in the case of the longitudinal shear modulus. The comparisons for the transverse shear modulus and the longitudinal Poisson’s ratio were uncertain. The agreements between the numerically predicted and experimentally determined stress–strain curves of the composite were found to be dependent on temperature and the type of loading. The experimental and numerical research data and the approaches presented in this work should significantly extend our knowledge of the effect of elevated temperatures on the mechanical behavior of unidirectional high temperature polymer matrix composites.