Influence of residual stresses and interfacial shear strength on matrix properties in fibre-reinforced ceramic matrix composites
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Zircon matrix composites, uniaxially reinforced with a variety of SiC fibres were fabricated in order to create composites with different interfacial properties. Interfacial properties were varied by changing the nature of fibre coatings. The effect of changes in interfacial shear strength on important matrix properties, such as hardness and fracture toughness, was studied on a micro-scale using the microindentation technique. In addition, the relative orientation of the indented cracks with respect to the fibres was varied to investigate the existence of anisotropic behaviour of the matrix. The results indicated that the crack growth in the matrix was influenced by the presence of residual radial and axial stresses, such that relatively higher crack lengths were seen in certain directions in the matrix with respect to other directions. This asymmetric nature of the crack formation upon indentation was the reason for the observed anisotropic fracture toughness of the matrix. The residual stresses also led to anisotropic hardness and a critical load for crack initiation in the matrix.
KeywordsResidual Stress Fracture Toughness Crack Initiation Anisotropic Fracture Matrix Composite
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