Damage-induced mechanical damping in phase-transforming composites materials

Abstract

We investigate the influence of stress-induced damage on the effective viscoelastic response of two-phase composites having constituents that undergo solid-solid phase transitions. Such composites are prone to experience damage near the interfaces separating phase-transforming inclusions and the non-transforming matrix. By accounting for inelasticity, temperature-induced phase transitions, and damage in the individual constituents and applying techniques of computational homogenization, we numerically show that the observed damage and resulting decrease in matrix stiffness can lead to significant changes in the overall, frequency-dependent damping and dynamic stiffness of the composite under time-harmonic two-dimensional loading. This is of particular interest since recent experiments and simulations hinted at increased composite damping due to metastable states of phase-transforming inclusions when embedded in a stiff matrix (so-called negative stiffness). Experiments also reported signs of matrix degradation, the causal mechanisms and consequences of which have not been investigated. The homogenized material response reported here reveals the interplay of material viscosity, matrix degradation, and structural transition, and illustrates how phase transformation and localized damage may lead to pronounced effective damping and stiffness variations.