Tensile properties of short fiber composites with fiber strength distribution

Abstract

The influence of fiber rupture, fiber pull-out and fiber tensile strength distribution on the post-cracking behavior of short-randomly-distributed fiber reinforced brittle-matrix composites has been analyzed using an approach based on the Weibull weakest-link statistics. The analysis led to the development of a predicting model for the composite bridging stress-crack opening displacement (σc - δ) law - a fundamental material property necessary for the analysis of steady-state cracking in the composites. The proposed σc - δ relationship can be used to relate the composite tensile and fracture properties to the microstructural parameters. The model revealed the importance of fiber strength distribution as described by the Weibull weakest-link statistics in governing the post-cracking response of the composite. The proposed model was able to reproduce the results of an earlier model for a limiting case where fiber tensile rupture was accounted for assuming a deterministic fiber tensile rupture strength. Model-predicted post-peak σc - δ curve was also in close agreement with those obtained from uniaxial tensile tests of a Kevlar fiber reinforced cementitious composite where fiber tensile rupture was reported. The model provided physical insights as to the micro-mechanisms controlling the post-cracking response of short-fiber reinforced brittle-matrix composites where fibers have a tensile strength distribution described by the Weibull weakest-link statistics.