Local Structural Damage Evaluation of a C/C–SiC Ceramic Matrix Composite

Abstract

Ceramic matrix composites (CMCs) are structural materials, which have useful properties that combine high strength at high temperatures with moderate toughness. Carbon fibers within a matrix of carbon and silicon carbide, called C/C-SiC, are a particular class of CMC noted for their high oxidation resistance. Here we use a combination of four-point bending and X-ray radiography, to study the mechanical failure of C/C-SiC CMCs. Correlating X-ray radiographic and load/displacement curve data reveals that the fiber bundles act to slow down crack propagation during four-point bending tests. We attribute this to the fact that strain energy is expended in breaking these fibers and in pulling fiber bundles out of the surrounding matrix material. In addition, we find that the local distribution and concentration of SiC plays an important role in reducing the toughness of the material.

In situ Observation of Compression Damage in a Three-Dimensional Braided Carbon Fiber Reinforced Carbon and Silicon Carbide (C/C-SiC) Ceramic Composite

“…X-ray computed tomography (XCT) provides three-dimensional observations of microstructure and may be applied during mechanical testing. Since the initial studies of Guvenilir (Guvenilir et al, 1997), in situ XCT has been applied to a wide range of materials including trabecular bone (Bay et al, 1999), wood (Forsberg et al, 2008), gypsum (Bouterf et al, 2014), graphite (Hodgkins et al, 2006; Marrow et al, 2016), ceramic matrix composites (Gao et al, 2016; Arhatari et al, 2017), and polymer matrix composites (Bie et al, 2017; Emerson et al, 2017; Garcea et al, 2017). The relative deformations between tomographs can be measured by digital volume correlation (DVC), which is a volumetric extension of the digital image correlation (DIC) method.…”

Failure Evaluation of a SiC/SiC Ceramic Matrix Composite During In-Situ Loading Using Micro X-ray Computed Tomography

“…In particular, synchrotron-based μ XCT has been used to resolve sequences of cracking in SiC/SiC under load (Saucedo-Mora et al, 2016) and at high temperatures (Bale et al, 2013). Anisotropy within the CMC, fiber microstructure, the distribution of SiC (and unreacted Si) within the matrix, and the presence of voids or cracks can be studied accurately using μ XCT (Baimpas et al, 2014; Frazer et al, 2015; Arhatari et al, 2017). Moreover, coupling between μ XCT and digital image correlation has been applied to quantifying stress distribution in SiC/SiC composites (Croom et al, 2017; Mazars et al, 2017).…”