Durability of a graphite/epoxy woven composite under combined hygrothermal conditions

The objective of this effort was to evaluate and model the effects of moisture, temperature and combined hygrothermal conditions on the strength and life of a graphite/epoxy woven composite material system. The material system specified is a candidate for use in an advanced subsonic aircraft engine, and the imposed environmental conditions were considered to be representative of engine service conditions. Fatigue and residual strength data showed that initial and residual tensile properties and fatigue life of the material were only minimally affected by any of the imposed environmental conditions for the fatigue stress levels considered in this study. Based on this data, it was shown a residual-strength-based life prediction approach could be used to model strength and life with reasonable results. Fatigue damage progression and accumulation were found to be dependent on testing environment, suggesting that more adverse effects of environment on strength and life may be manifested for other types of loading (i.e., off-axis loading).