Synchrotron X-ray study of micromechanics of Ti/SiC_f composites with fibres containing defects introduced by laser drilling

High spatial resolution synchrotron X-ray strain measurement and tomography have been performed on Ti/SiC_f composite samples containing controlled distributions of fibre defects introduced by laser drilling. The objective of the study was to gain an understanding of the micromechanics of stress and damage development that occur on progressive straining in the vicinity of damaged fibres. The composite samples were fabricated to contain precisely located fibre defects so that the redistribution of load from damaged fibres to neighbouring ones could be investigated. The interfacial characteristics in these regions, such as the shear stresses at the interface, have been studied. Axial strain measurements were made along each fibre during incremental loading using a small X-ray spot size to obtain strain profiles along each fibre and in the neighbouring matrix. Lower interfacial shear stresses have been found near the holes introduced prior to fabrication than near cracks formed during loading. The interface performance has been interpreted in the light of simple models. Cracking sequences have been observed in detail by X-ray tomography as a function of straining.