Estimation of the hygro-elastic behavior of polymeric composites during moisture aging considering hygromechanical coupling

This study aims to combine, using a numerical tool, different phenomena of hygromechanical coupling in a unidirectional carbon/epoxy composite and to compare the results obtained with the cases where these couplings are considered separately. The first case of coupling considers the effect produced by the mechanical state on the diffusive behavior of the material. This was accomplished using the free volume theory, which links the trace of the matrix strain tensor to the moisture absorption capacity and the diffusion coefficient. The second case takes into account plasticization, that is, the effect of humidity on the mechanical properties of composites, without modifying the diffusion parameters. Finally, these two mechanisms are combined in a third configuration, which represents the original contribution of this present work. The results include the water content profiles, the diffusion coefficient, the transverse Young's modulus, the transverse hygroscopic expansion coefficient, as well as the induced local mechanical states. The interest of the work carried out is to pave the way for the extension to more complex materials, such as plant fiber biocomposites, in which the water absorption by the hydrophilic fibers should not be neglected anymore.