Tensile properties of short fiber composites with fiber strength distribution

The influence of fiber rupture, fiber pull-out and fiber tensile strength d istribution on the post-cracking behavior of short-randomly-distributed fib er reinforced brittle-matrix composites has been analyzed using an approach based on the Weibull weakest-link statistics. The analysis led to the deve lopment of a predicting model for the composite bridging stress-crack openi ng displacement (sigma (c) - delta) law-a fundamental material property nec essary for the analysis of steady-state cracking in the composites. The pro posed sigma (c) - delta relationship can be used to relate the composite te nsile 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 e arlier model for a limiting case where fiber tensile rupture was accounted for assuming a deterministic fiber tensile rupture strength. Model-predicte d post-peak sigma (c) - delta curve was also in close agreement with those obtained from uniaxial tensile tests of a Kevlar fiber reinforced cementiti ous 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 h ave a tensile strength distribution described by the Weibull weakest-link s tatistics. (C) 2001 Kluwer Academic Publishers.