Evaluation of the Effect of Voids on Matrix-Dominated Strength of CFRP Based on Void Shape Characterization Using X-ray CT

Abstract

In this study, void distributions in unidirectional carbon fiber-reinforced plastic (CFRP) laminates were measured using X-ray computed tomography (CT), and the stress concentrating effects of the voids on the reduction of the CFRP matrix-dominated strength were modeled. We first investigated the statistical features of the void sizes, geometrical shapes, and locations by analysis of the X-ray CT three-dimensional images. The natural logarithms of the void sizes showed a three-dimensional normal distribution; consequently, the void shapes and aspect ratios were correlated. Next, using the measured results regarding the voids, the stress concentration effect on the reduction of transverse tensile strength was modeled based on the Weibull model considering the volume dependence of strength. From the results, we attributed the decrease in the matrix-dominated strength with increases in void volume fraction to the increase in stress concentration volumes accompanying the increased number of voids.