Damage induced room temperature creep of titanium matrix composites

Experimental results indicate that titanium matrix composites (TMC) can exhibit room temperature creep at moderate stress levels. Also, room temperature creep has been observed to initiate in monolithic titanium (Ti-15-3) at stress levels in excess of the proportional limit. A micromechanical model that explicitly includes fiber/matrix interfacial debonding has been used to predict how debonding affects the creep response of unidirectional silicon carbide/titanium (SiC/Ti) composites subjected to transverse tensile loading. The model clearly shows that a redistribution of stress from the fiber to the matrix occurs during debonding. The elevated local stresses in the matrix increase the susceptibility of the composite to creep. Room temperature creep in a completely debonded composite is predicted to initiate at an average composite stress that is 60% below the stress required to initiate creep in a perfectly bonded composite and 50% below that required to initiate creep in monolithic Ti-15-3.