Variational estimates for the elastic properties of polycrystalline solids with compliant intergranular bonding

M. I. IDIART; VALENTIN GALLICAN

Galway

Conferencia; 11th European Solid Mechanics Conference; 2022

Many energetic solids of technological interest are aggregates of micrometric particles or grains cemented together by a compliant binding phase \cite{Chen2007}. Prominent examples include polymer-bonded triaminotrinitrobenzene and cyclotetramethylene-tetranitramine. Despite occupying a low fraction of the total volume, the binding phase can play a central role on the overall thermomechanical behavior and sensitivity of the solid. In high-energy systems the binding phase can be regarded as an interphase of vanishing thickness so that the aggregate can be conceived as a polycrystalline solid with compliant grain boundaries \cite{Luscher2018}. A micromechanical model for the overall elastic properties of such material systems is here confected by means of a self-consistent approach. The model is restricted to isotropic morphological textures but can account for arbitrary crystallographic textures. In contrast to similar models already proposed in the literature \cite{Luscher2018,Zecevic2021}, the present model relies on rigorous variational approximations that $(i)$ reproduce exact results for material systems with weakly anisotropic but otherwise arbitrarily large grain-boundary compliances, and that $(ii)$ can easily accommodate dissipative processes occurring at the grain boundaries in a thermodynamically consistent manner.