Response of SiC/Ti under Combined Loading. Part I: Theory and Experiment for Imperfect Bondin

Results from cyclic multiaxial tests on unidirectional [04] and angle-ply [±45], silicon carbide/titanium (SiC/Ti) tubular specimens are compared with theoretical predictions from a micromechanical model that includes imperfect bonding between the fiber and matrix. Comparison of theory and experiment indicates that damage to the fiber/matrix interface often is a major factor in the stress-strain response of SiC/Ti composites. The axial shear (torsional) response of a [04] tube displayed a distinct knee associated with damage at the shear stress of 276 MPa (40 ksi). Transverse tensile (internal pressure) loading of a [04] tube and axial tensile loading of a [±45], tube resulted in inelastic deformation due to damage well before initial yielding was predicted to occur in perfectly bonded composites. Substantial differences were observed in the effects of damage on the response of [04] and [±45], tubes subjected to combined loading.