Statistical Analysis of Strain Rate Dependency of the Mechanical Properties of Unidirectional CFRE Materials

Abstract

With the aim of finding new materials having high stiffness to density ratio, carbon fiber composite materials have gained popularity as alternatives to traditional high-stiffness and high-density materials. This work investigates the dependency on strain rate of some mechanical properties of unidirectional carbon fiber reinforced epoxy, CFRE. The composite laminates were fabricated at fiber orientations of 0° (dubbed type 1) while others at 90° (dubbed type 2). Statistical analysis (using Minitab® software) has been applied to determine the statistical significance (modulus at confidence interval varying from 5% to 10%) of the effect of strain rate on composite material response and strength. Both type 1 and type 2 composite laminates were tested at several levels of flexural strain rates varying from 1.8*10−5 s−1 to 7.8*10−3 s−1. For type 1 and type 2 laminates, the flexural fracture stress values were found to increase around 4.5% and 8.6%, respectively, for the studied range of strain rates. It was also found that the flexural modulus of elasticity increased for both 0° and 90° increase in order of 5% and 10%, respectively, for type 1 and type 2 laminates over the strain rate range. This was evidenced by the increase in the variance of the experimentally collected flexural strength values with increasing operating strain rate.