Creep and physical aging in a polymeric composite: Comparison of tension and compression

To help address the lack of engineering data on the time-dependent behavior of advanced polymeric composites, a combined experimental and analytical research program was initiated to investigate the similarities and differences of the effects of physical aging on creep compliance of IM7/K3B composite loaded in tension and compression. Recently developed novel experimental apparatus and methods were employed to test two matrix dominated loading modes, shear and transverse, for two load cases, tension and compression. The tests, run over a range of sub-glass transition temperatures, provided material constants, material master curves and aging related parameters. Assessment of these new results indicated that although trends in the data with respect to aging time and aging temperature are similar, differences exist due to load direction and mode. An analytical model proposed previously by the authors for tension loading was used for predicting long-term tension and compression behavior using short-term data as input. These new studies indicated that the model worked equally as well for the tension or compression loaded cases. Comparison of the loading modes indicated that the predictive model provided more accurate long-term predictions for the shear mode as compared to the transverse mode. Parametric studies showed the usefulness of the predictive model as a tool for investigating long-term performance and compliance acceleration due to temperature.