Effect of Fatigue Damage in Woven Composites on Thermo-Mechanical Properties and Residual Compressive Strength

The long term mechanical and thermal fatigue of a Celion G30-500/PMR-15 woven composite system is investigated to study the interrelationship between thermo-mechanical properties, namely the thermal expansion coefficent (TEC) and the compressive strength. Qualitative trends in the experimental data generated by either thermal or mechanical loadings are shown to be similar to properties predicted by a shear lag based model. Residual compressive strength measurements (IITRI fixture) conducted on specimens subjected to tension-tension fatigue cycling indicate that this material property is sensitive to cracks and delaminations which form during mechanical cycling. Measured compressive strength degradation is as large as 49% for this material undergoing mechanical fatigue cycling with TEC degradation as large as 61%. Experimental results show that a correlation exists between TEC measurements and compressive strength. This correlation suggests that TEC measurements may be used as a damage evaluation technique.