The composite material specified herein is military unique because it is the only proven material used in aging aircraft replacement parts. This composite has been increasingly accepted as an engineering material for the design and fabrication of aerospace structural components, particularly aeropropulsion structural components. Material procured in accordance with this specification is intended for use in airframe, aerospace, and similarly related primary or secondary load-bearing structures where high stiffness and strength-to-weight ratios are required. Historically PMR-15 resin has been employed but comparable resin systems may be utilized. Polyimide (PMR-15) composite material has been extensively characterized in the NASA Composites for Advanced Space Transportation Systems (CASTS) Program, and is used in aircraft engine hardware such as cowls, nozzle flaps, and ducts.

A design allowables test program was conducted on graphite/polyimide composites by NASA (NASA CR-165840) to establish material performance over a 116°K (−250°F) to 589°K (600°F) temperature range. Effects of aging, thermal cycling and moisture were also evaluated. Tension, compression and in-plane shear properties were determined for uniaxial, pseudoisotropic and ± 45 degree laminates. Test results show sufficient strength and stiffness to substantiate graphite/polyimide composites as an acceptable structural material for high temperature structural applications.