Experimental Observations on Composite DamageEvolution Under Extreme Temperatures

摘要

The objective of this work was to develop a predictive capability for the onset of free-edgerndelamination in composite laminates subjected to isolated or combined thermal and mechanicalrnloads. The material system investigated was a carbon fiber-reinforced toughened bismaleimiderncomposite, IM7/977-3.rnSpecimens of [ ±30/90]S laminate were tested to determine the onset of delamination under isolatedrnor combined mechanical and thermal loads. Delamination was detected from acoustic emission inrnconjunction with incremental loading and unloading experiments, and confirmed from microscopicrnexamination of polished specimen edges. The interlaminar free-edge stresses were analyzed using arnglobal-local model. The results of this stress analysis were compared with the experimental results.rnThe material elastic properties as well as the ply transverse strength and interlaminar shearrnstrength are significantly influenced by the cryogenic temperatures selected for this study. While thernresidual stresses increase with decreasing test temperature, so do the composite transverse and shearrnstrengths, and these two effects compete in their influence on the stress to initial delamination.