Thermodynamics of Viscous Damping in Inelastic Fiber Composites

Abstract

Recently, viscoelastoplastic fiber-reinforced shell structures and thermodynamical behavior of inelastic isotropic solids have been studied. The present paper is concerned with the thermodynamics of inelastic glass fiber composites exhibiting significant viscous damping characteristics combined with plastic deformations. The construction of a theory describing the rate-dependent inelastic behavior must be based on irreversible thermodynamic processes since the viscous damping is greatly affected by temperature changes. However, such an attempt encounters a basic difficulty in the form of a free energy function which, in general, is not smooth. In the present study, an incremental theory is developed such that anisotropic properties of the material associated with dissipative process may be defined within a small discretized time domain. The explicit material kernels representing rate-dependent inelastic behavior are nonexistent. It is possible, however, to propose a form of free energy function considered smooth within a small time increment which contains all possible sources of energy depicting properties of elasticity, viscosity, and plasticity, under nonequilibrium thermodynamic processes. The present study is a step toward practical applications of rational thermodynamic theory to rate-dependent inelastic anisotropic composite structures. The finite element method is employed to obtain extensive numerical solutions.