Characterization of graphite fiber/polyimide composites for RLV applications

摘要

Polyimide matrix composites have been used successfully in aeronautic engine applications at temperatures of 290-315°C. Extending these materials to Reusable Launch Vehicle applications will require higher operating temperatures for shorter duration. In this paper an eight-harness satin weave T650-35/PMR-II-50 composite has been tested at temperatures of 260-480°C. Composite quality was characterized through destructive and nondestructive techniques. Uniaxial tension, creep, and tension-tension fatigue tests were conducted in the temperature range of 260-480°C on dry specimens. Tensile strength degradation at temperatures below 480°C was minimal; the elastic modulus was essentially constant below 385°C. Fatigue results presented include stress life data and the cyclic degradation of tensile and compressive moduli. Furthermore, the temperature for onset of steam delamination was determined as a function of moisture content and heating rates (0.6°C/min to 6°C/min). The tensile modulus, compressive modulus and residual tensile strengths from both dry & moisture-saturated specimens were similar when tested below the macroscopic delamination temperature.