Joshi Research Group

Materials and Mechanics Research

Size-effects in crystal plasticity Internal stresses in FCC metals

Moisture-induced degradation of reinforced polymers

Polymers, natural or synthetic, are often subjected to residual stresses under varying hygroscopic conditions, due to the difference in the moisture expansion coefficients between the inclusion and the matrix. Moisture ingress may assist the degradation of composites used in, for example, wind energy or marine structures, dental composites and similar hostile conditions. In this work, we investigate the response of fiber-reinforced polymers under transient hygro-mechanical conditions at two microstructural length-scales. In this work, we demonstrate the role that fiber distribution plays in the evolution of overall damage debonding at the matrix-inclusion interfaces due to moisture-induced stresses, using finite element based micromechanics. Motivated by experimental observations, we incorporate the interface behavior that degrades with the local moisture concentration. The moisture and mechanical transients provide synergistic conditions for the evolution of debonding, under both the sequential and simultaneous loading. The results show that fiber clustering strongly affects the moisture diffusion characteristics of the RVEs that in turn hurt the overall load carrying capacity of a composite due to aggravated damage. The strong dependence of the moisture-induced damage evolution on the fiber arrangement suggests that one should not resort to using simplistic unit cell models that assume regular fiber arrangements.


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