Material strength knock-down resulting from multiple randomly positioned voids

Abstract

To give a better understanding of the impact of manufacturing defects and porosity on the strength of composite components, the strength knock-down of a material containing multiple voids or flaws is characterized. The voids are modeled as elliptical holes with equal size but random position and orientation on a 2D square domain, and modeled using a semi-automated Finite Element approach. Edge traction forces apply a uniform nominal shear stress, and a relatively coarse mesh is chosen in order to average out highly localized stresses and reveal trends in stress intensity as porosity is increased. A Weibull analysis of the localized peak stresses for different levels of porosity is undertaken. It was found that although void shape and percentage porosity levels play a role in the strength reduction, the critical factor is the variation of distance between the voids. Void distributions which are more homogeneous exhibit ‘defender hole’ stress shielding characteristics and show significantly less strength reduction.