No abstract

To simulate the evolution process of interfacial debonding between particle and matrix, and to further estimate its effect on the overall elastic behavior of particle-reinforced composites, a two-level microstructural-effective damaged model is developed. The microstructural damage mechanism is governed by the interfacial debonding of reinforcement and matrix. The progressive damage process is represented by the debonding angles that are dependent on the external loads. For those debonded particles, the elastic equivalency is constructed in terms of the stiffness tensor. Namely, the isotropic yet debonded particles are replaced by the orthotropic perfect particles. The volume fraction evolution of debonded particles is characterized by the Weibull’s statistical approach. Mori-Tanaka’s method is utilized to determine the effective stiffness tensor of the resultant multi-phase composites. The proposed constitutive framework is developed under the general three-dimensional loading condition. Examples are conducted to demonstrate the capability of the proposed model.

The elastic moduli of tumors change during their pathological evolution. Elastographic imaging has potential for detecting and characterizing cancers by mapping the stiffness distribution in tissues. In this paper a micromechanics-based analytical method was developed to detect the location, size, and elastic modulus of a tumor mass embedded in a symmetric two-dimensional breast tissue. A closed-form solution for the strain elastograms (forward problem) was derived. A computational algorithm for the inverse problem was developed for the detection, localization, and characterization of a heterogeneous mass embedded in a breast tissue. Numerical examples were presented to evaluate the proposed method's performance. The detectability of a tumor mass was estimated with respect to lesion location, size, and modulus contrast ratio. It was shown that the micromechanics theory provides a powerful tool for the diagnosis of breast cancer.

SUMMARYA micromechanics-based elastoplastic and damage constitutive model is proposed to predict the overall mechanical behaviour of particle-reinforced metal matrix composites. Unidirectionally aligned spheroidal elastic particles, some of which contain penny-shaped cracks, are randomly distributed in the elastoplastic metal matrix. These imperfect particles, attributed to progressive particle cracking, are modelled by using the double-inclusion concept. An ensemble-volume averaged homogenization procedure is employed to estimate the e ective yield function of the damaged composites. The associative plastic ow rule and the hardening law are postulated based on the continuum plasticity theory. The underlying damage evolution of particles is considered in accordance with the Weibull's statistical function to characterize the varying probability of reinforcement cracking. The elastoplastic mechanical behaviour of particulate composites under uniaxial loading conditions is simulated and compared with available experimental results.

A micromechanical damage model is proposed to predict the effective elastoplastic behavior of ductile composites containing randomly dispersed particles. The interfacial debonding between particles and the matrix is considered as the primary micromechanical damage mechanism. The debonded isotropic elastic reinforcements are replaced by equivalent anisotropic elastic inclusions. The interfacial debonding process is simulated by three-dimensional debonding angles. After the local stress field in the matrix is calculated, the homogenization averaging procedure is employed to estimate the effective elastic stiffness and yield function of the composites. The associative plastic flow rule and the isotropic hardening law are postulated based on the continuum plasticity theory. As applications, the overall elastoplastic and damage constitutive behavior of the composites under various loading conditions is numerically simulated and compared with available experimental results.