LIFETIME EXTRAPOLATION OF PMR-15 AND LARC(TM)-160 GRAPHITE COMPOSITES

Small unidirectional composite specimens of two nadimide-terminated thermosetting polyimide resins were aged in circulating air ovens at various temperatures for up to 25,000 hours. Criteria for weight loss and loss in short-beam shear strength were used to define useful lifetimes as a function of temperature. An Arrhenius relationship could be used to extrapolate the data to lower temperatures and longer times. Both LaRC(TM)-160/Celion 6000 and PMR-15/Celion 6000 graphite composites gave extrapolated use temperatures of 160-180-degrees-C for a 60,000-hour life. Apparent activation energies were 12-20 kcal/mol.