CREEP AND CREEP-FATIGUE BEHAVIOR OF CONTINUOUS FIBER-REINFORCED GLASS-CERAMIC MATRIX COMPOSITES

The flexural creep acid creep strain recovery behaviour during creep-fatigue tests of a cross-ply SiC fibre reinforced Barium Magnesium Aluminosilicate glass-ceramic matrix composite was investigated at 1100 degrees C in air. Only heat-treated samples (1 h at 1100 degrees C) were tested. Stress levels of 90, 105 and 120 MPa were examined to produce low strains (<0.4%). A continuously decreasing creep strain rate with values between 1.6 x 10(-6) s(-1) to 4.7 x 10(-8) s(-1) at 120 MPa was observed with no steady-state regime. Extensive viscous strain recovery was found upon the unloading period during the short-duration cyclic creep (creep-fatigue) experiments. The creep strain recovery was quantified using strain recovery ratios. These ratios showed a slight dependence on the stress and cyclic loading frequencies investigated. The crept composites retained their ''graceful'' fracture behaviour after testing indicating that no (or limited) damage in the matrix was induced during creep and creep-fatigue loading.