Response of SiC/Ti tubes under biaxial loading in the presence of damage

This paper presents the results of a combined experimental and theoretical investigation of the inelastic response of unidirectional [0] and angle-ply [±45]_s, SiC/Ti tubes subjected to axial, torsional and combined axial/torsional loadings. The test program consisted of a series of axial and torsion tests, to sequentially higher load levels, on tubes fabricated using SCS₆ silicon carbide fibers and Ti-15-3 titanium matrix. The axial and shear response was monitored throughout the entire load history. This provided the opportunity to study the axial and shear response at different levels of interfacial damage, matrix plasticity and combined load states. The experimentally measured axial and shear response, and initial yield stresses were compared with micromechanics predictions generated with different degrees of imperfect fiber/matrix bonding. The results suggest that damage to the fiber/matrix interface occurs prior to matrix plasticity and actually accelerates the onset of initial matrix yielding.