COMPRESSIVE CREEP OF IM7 K3B COMPOSITE AND THE EFFECTS OF PHYSICAL AGING ON VISCOELASTIC BEHAVIOR/

An experimental study was undertaken to establish the viscoelastic beh avior of IM7/K3B composite in compression at elevated temperature. Cre ep compliance, strain recovery and the effects of physical aging on th e time dependent response was measured for uniaxial loading at several isothermal conditions below the glass transition temperature (T-g). T he IM7/K3B composite is a graphite-reinforced thermoplastic polyimide with a T-g of approximately 240 degrees C. In a composite, the two mat rix-dominated compliance terms associated with time dependent behavior occur in the transverse and shear directions. Linear viscoelasticity was used to characterize the creep/recovery behavior, and superpositio n techniques were used to establish the physical aging related materia l constants. Creep strain was converted to compliance and measured as a function of test time and aging time. Results included creep complia nce master curves, physical aging shift factors and shift rates, The d escription of the unique experimental techniques required for compress ive testing is also given.