UC Santa Barbara

© 2014 The American Ceramic Society. This article addresses the effects of small holes (1-2 mm in diameter) on the tensile properties of a woven C/SiC composite. Holes are introduced by one of two methods: by insertion of fugitive rods into the woven preform before adding the matrix or by drilling after panel fabrication. The tensile strength exhibits only a weak sensitivity to the presence of holes, regardless of the manner in which the holes are introduced. Nevertheless, woven holes appear to be somewhat less detrimental to strength. The effects are attributed to the fact that the tows in specimens with woven holes are locally intact and thus contribute to load-bearing. Full-field strain maps reveal strong spatial periodicity, reflecting the underlying crack pattern and weave geometry. Even when averaged over lengths equal to the unit cell dimensions, the strains exhibit periodicity, with a wavelength dictated by the unit cell dimensions. When holes are present, the strain patterns reflect a convolution of the effects of weave geometry and strain concentrations near the holes. The results have implications for development of high-fidelity models for these composites: notably, in selection of a suitable representative volume element and for modeling schemes that capture the stochastic nature of cracking.