Effect of Isothermal Aging on Ultimate Strength of High-Temperature Composite Materials for SST Structures

Abstract

The objective of this experimental study was to evaluate the effect of iso-thermal aging on the ultimate strength of three kinds of carbon/high-temperature composite materials, i.e., G40-800/5260 and MR50K/MR2000N bismaleimide composites and T800H/PI-SP amorphous thermoplastic polyimide composite. These materials are current candidate structural materials for a supersonic transport of the next-generation. The hole-notched and unnotched panels, before being machined to specimens, were isothermally aged at 120°C and 180°C for up to 15,000 hours. Static tests at room and elevated temperatures before and after thermal aging provided the open-hole tensile, open-hole compressive, and short beam shear strengths. Moreover, the effects of five oxidation resistant treatments on open-hole compressive strength at 180°C were investigated after isothermal aging of 5,000 hours at 180°C. The test results clarified the effects of isothermal aging on ultimate strengths and oxidation resistant treatments on open-hole compressive strength. Moreover, the possibility of developing an accelerated aging test method is discussed using a modified Larson-Miller type equation.