A comparative study of void characteristics on the mechanical response of unidirectional composites

Defects in composite structures, such as voids, cannot entirely be avoided during the manufacturing, and have detrimental effect on the damage behavior and mechanical properties. The main characteristics of voids in composites are void content, shape, size, location and distribution. To investigate the effect of void characteristics on the failure mechanisms and mechanical properties of unidirectional composites, a non-conservative modeling method based on separation axes is proposed to generate representative volume element with arbitrary local microstructures, then the effect of void characteristics on the mechanical responses of unidirectional composites is studied by computational mechanics. Four types of typical voids are investigated to reveal the effect of void shapes and locations on failure mechanism, the damage evolution processes and mechanical response under various loading cases are analyzed comprehensively. It was found that the presence of interfacial voids modified the trend of the stress–strain curve under shear loading and almost all voids led to a significant reduction in the failure strength under transverse and shear loadings. Besides, the influence of void characteristics in the onset and propagation of damage throughout the microstructure is obviously different. Finally, the predictions by present model are compared with analytical method and available experimental data, good overall agreement is found.