Papers by Author: Qi Chang He

Abstract: Starting from the requirement that the principle of determinism be satisfied, two constitutive inequalities are derived for one-dimensional strain- and stress-based continuum damage models. The one-dimensional constitutive inequality corresponding to the strain-based formulation turns out to be much less restrictive than the one associated to the stress-based formulation and is extended to the three-dimensional case. This extension gives a general constitutive inequality for the damage of elastic-brittle materials.

Abstract: This work is concerned with a versatile and efficient model for estimating the effective moduli of isotropic composites consisting of isotropic phases whose microstructure may be of matrix-inclusion type, disordered or intermediate. This extended version of generalized self-consistent model (GSCM) is built by inserting a composite sphere embedded in an infinite unknown effective medium has the core made of the unknown effective medium and coated by the constituent phases. The volume fraction of the constituent phases in this composite sphere is the characteristic parameter of the relevant microstructure. By imposing the an energy equivalency condition, the equations thus obtained to estimate the effective bulk and shear moduli involve the microstructural parameter which turns out to be capable of describing in some sense how far a microstructure is from the host matrix/inclusion morphology

Abstract: The purpose of this work is to extend the equations of linear poroelasticity to the case of materials with nanopores. We consider a model of microstructure which corresponds to an assemblage of hollow spheres saturated by a fluid. The solid phase is linearly elastic and isotropic; pores are assumed to be of nanometric size. To account for the pore surface stresses, the Young-Laplace model is used. The nanopore size effects on the effective bulk modulus, Biot’ modulus and coefficient are shown. When pores are sufficiently large, the classical relations of linear poroelasticity are retrieved.

Abstract: In this work, we derive a general piezoelectric interface model by using a coordinate-free asymptotic approach. Next, this interface model is applied to the homogenization of fibrous piezoelectric composites. The overall piezoelectric properties are calculated and compared to the ones obtained by using the three-phase model.