The buckling and postbuckling responses of viscoelastic-layered composites are investigated using finite-element simulations. These composites consist of alternating layers of a stiff elastic constituent and of a soft viscoelastic constituent. In response to compressive loads in the layer direction, elastic instabilities significantly affect the finite deformation mechanics of these composites. The dependence of the critical strain and critical wavenumber on strain rate is analyzed. In the postbuckling regime, the wavenumber of the mode of deformation is found to be highly dependent on strain rate and time and can be used to identify three different regimes that depend on the volume fraction of the stiff constituent. Interestingly, a transition from a wrinkling mode to a longwave mode can be observed when the strain rate is varied for moderate volume fractions of the stiff material. Analytical formulae for the buckling and postbuckling of the elastic-layered composites are used to interpret numerical results obtained for viscoelastic-layered composites. Viscoelastic-layered composites exhibit a wide range of rate-dependent mechanical behavior and could have applications in vibration damping and acoustic metamaterials.

This paper investigates the nonlinear mechanics of layered composites that include a stiff elastic constituent and a soft viscoelastic constituent. Layered composites buckle with an infinite wavelength at small compressive strains in the case of a high volume fraction of the stiff constituent (the non-dilute case). An iterative algorithm is derived for the finite deformation of viscoelastic non-dilute layered composites with neo-Hookean phases. After validation by comparison to nonlinear finite element simulations, we analyze the effect of initial layer direction, strain rate, and prestrain on the response to timedependent prescribed compressive strains. Interestingly, these composites have both a very high stiffness prior to buckling and a large energy dissipation capacity in the postbuckling regime. When these composites are subjected to cyclic strains of small amplitude, the effective stiffness and damping properties can be tuned by orders of magnitude by adjusting the prestrain.

A model of damage evolution in austenitic stainless steels under creep loading at elevated temperatures is proposed. The initial microstructure is idealized as a space-tiling aggregate of identical rhombic dodecahedral grains, which undergo power law creep deformation. Damage evolution in the form of cavitation and wedgecracking on grain boundary facets is considered. Both diffusion-and deformationdriven grain boundary cavity growth are treated. Cavity and wedge-crack length evolution is derived from an energy balance argument that combines and extends the models of Cottrell [1], Williams [2] and Evans [3]. The time to rupture predicted by the model is in good agreement with published experimental data for a type 316 austenitic stainless steel under uniaxial creep loading. Deformation and damage evolution at the microscale predicted by the present model are also discussed.