HYGROMECHANICAL COUPLING AND TRANSVERSE FAILURE OF LAMINATED COMPOSITES

摘要

The coupling between water diffusion and the mechanical state of Graphite-Phenolic (GPh)rncomposites was studied both analytically and experimentally. The aim of the research was tornassociate the apparent decrease in the strength of GPh specimens during a drying process, with thernbuild-up of the hygromechanical stresses, caused by the high shrinkage strains.rnRecently, several thermodynamically-based coupled models were published, but none of them wasrnexperimentally tested. Using the symmetry of the GPh specimens, we were able to simplify thesernmodels, allowing solving and validating the coupled governing equations for both concentrationrnand stress fields. Experiments included gravimetric and strain measurements of specimens underrnvarious conditions. Flexure tests were used to characterize the composite’s failure strength duringrnthe drying process. Using an appropriate failure criterion, we demonstrated that the decrease in therncomposite’s strength can be related to the increase of the calculated hygromechanical stress.