INFLUENCE OF MONOTONIC OR OSCILLATING STRESS TESTS ON THE WORK-HARDENING RATE IN PABM RESIN

The influence of creep and oscillating stress tests on the nucleation rate of 'plasticity' defects is investigated in the case of poly(aminobismaleimide) (PAMB) thermoset resin by measuring the work-hardening rate K in the pre-yield stage. In both cases, after 12h tests, K is multiplied by factor 6, V//0 is divided by a factor 5, and DELTA epsilon //p, the variation of the non-elastic strain, follows a logarithmic law with time. Thus, the creep is similar to the alpha -creep observed in metals at low temperatures, where the defect nucleation is not thermally activated. The 'fatigue' test differs from the creep test in having a DELTA epsilon //p value twice as large, because of dynamical recovery.