Time-dependent reduction of tensile strength caused by interfacial degradation under constant strain duration in UD-CFRP

The residual strength in UD-CFRP was measured after being subjected to constant strain. In order to quantify the strength reduction, the time-dependent variation of interfacial stress-transfer capacity in a single-fiber composite specimen was quantitatively studied using micro-Raman spectroscopy. The analysis originally included a decrease of interfacial frictional stress due to a relaxation of interfacial radial stress and a time-dependency of an interfacial debonding propagation criterion, based on the conventional viscoelastic shear-lag model. The residual strength in UD-CFRP after enduring long-term loading was then analyzed using the global load sharing model with the results of variation of the interfacial property.