© 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.

We present a new, 3D description of crust and upper mantle velocity structure in southern California implemented as a Unified Structural Representation (USR). The USR is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity (Vp, Vs) measurements and incorporates the locations and displacement of major fault zones that influence basin structure. These basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure, which were subsequently iterated and improved using 3D waveform adjoint tomography. A geotechnical layer (GTL) based on Vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component. The resulting model provides a detailed description of the structure of the southern California crust and upper mantle that reflects the complex tectonic history of the region. The crust thickens eastward as Moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust. Deep sedimentary basins and underlying areas of thin crust reflect Neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late Pliocene. To illustrate the impact of this complex structure on strong ground motion forecasting, we simulate rupture of a proposed M 7.9 earthquake source in the Western Transverse Ranges. The results show distinct basin amplification and focusing of energy that reflects crustal structure described by the USR that is not captured by simpler velocity descriptions. We anticipate that the USR will be useful for a broad range of simulation and modeling efforts, including strong ground motion forecasting, dynamic rupture simulations, and fault system modeling. The USR is available through the Southern California Earthquake Center (SCEC) website (http://www.scec.org).