TIME-DEPENDENT BEHAVIOR OF A GRAPHITE THERMOPLASTIC COMPOSITE AND THEEFFECTS OF STRESS AND PHYSICAL AGING

Experimental studies were performed to determine the effects of stress and physical aging on the matrix dominated time-dependent properties of IM7/8320 composite. Isothermal tensile creep/aging test techniques developed for polymers were adapted for testing of the composite mater ial. Time-dependent transverse (S-22) and shear (S-66) compliance's fo r an orthotropic plate were found from shortterm creep compliance meas urements at constant, sub-T-g temperatures. These compliance terms wer e shown to be affected by physical aging. Aging time shift factors and shift rates were found to be a function of temperature and applied st ress.