Influence of void microstructure on the effective elastic properties of discontinuous fiber-reinforced composites

This study investigates the influence of void microstructure on the effective elastic properties of high fiber volume fraction discontinuous fiber-reinforced composites with randomly oriented fibers. A void microstructure is characterized by using parameters such as the number of voids, void volume fraction, void Aspect Ratio and void size distribution. In order to overcome the difficulties associated with the creation of high fiber volume fraction representative volume element models containing voids, a novel automation program called "ArtiComp" is developed. This program is used to generate representative volume element models of discontinuous fiber-reinforced composites containing randomly oriented straight fibers, curved fibers and spheroidal voids. The effective properties of discontinuous fiber-reinforced composites are computed using a finite element-based micromechanics approach. For comparison, the Mori-Tanaka method is used to compute the effective properties of unidirectional discontinuous fiber-reinforced composites and then orientation averaging is performed on these properties to obtain the effective properties of discontinuous fiber-reinforced composites with randomly oriented fibers. The comparison shows that the finite element predicted properties are stiffer than the analytically predicted properties. The results indicate that the finite element predicted properties are dependent on the number of voids used to represent the void volume. It is seen that the effective properties significantly decrease when void volume fraction is increased. The void Aspect Ratio and void size distribution are found to have a negligible influence on the effective properties. Finally, it is observed that straight fiber composites with voids perform better than the corresponding curved fiber composites with voids.