Micromechanics and effective thermo-mechanical damage and deformation responses of composite materials

The primary objective of this research activity is to explore the effective thereto-mechanical deformation responses of fiber and particle reinforced composites by modifying and extending the available micromechanical framework.;In Chapter 3, by considering the progressive interfacial fiber-debonding, the elastoplastic damage formulation is proposed to predict the overall transverse deformation behavior of continuous elliptical-fiber reinforced metal matrix composites. Specifically, the explicit, exact exterior-point Eshelby's tensor for an elliptical fiber is presented to investigate its effects upon inelastic responses of composites due to the cross-sectional shapes of fibers.;Second, on the foundation of the probabilistic micromechanical framework developed in Chapter 3, and to investigate the manufacturing process-induced residual stresses, the thermal residual stresses are taken into account through the concept of thermal eigenstrain in Chapter 4. Employing the micromechanical approximation, the overall stress-strain responses and effective yield function are formulated with the thermal eigenstrain. When comparing with available experimental data, the significant effects of the thermal residual stresses are discussed.;Thirdly, to predict the particle-size dependent deformation responses of particle-reinforced metal matrix composites, the probabilistic size-dependent damage evolutions and micromechanics-based phenomenological dislocation theory are incorporated into the micromechanical framework in Chapter 5. To predict the overall elastoplastic damage behavior of composites, a size-dependent hybrid effective yield function is proposed based on the ensemble volume averaging and the modified matrix yield strength. Comparisons between the theoretical predictions and the available experimental data exhibit the capability of proposed framework.;Subsequently, in Chapter 6, a micromechanical framework is presented to predict the effective deformation responses of particle-reinforced composites with high particle-volume fractions. By making use of the exterior-point Eshelby tensor and the equivalence principle with the pair-wise particle interactions, the interacting eigenstrain is explicitly derived. Accordingly, the near-field particle interactions are accounted for in the effective mechanical behavior of spherical-particle reinforced composites. In contrast to those higher-order formulations in the literature, the proposed micromechanical formulation can accommodate the anisotropy of reinforcing particles and can be employed for multi-phase composites.;In Chapter 7, based on the micromechanical framework developed in Chapter 6, a higher-order micromechanical framework is proposed to predict the overall elastic mechanical deformation behavior of continuous-circular fiber reinforced composites with high volume fractions. A series of comparisons with the available experimental data for the isotropic and anisotropic fiber reinforced composites illustrates the predictive capability of the proposed framework.;Finally, Chapter 8 summarizes the presented research and discusses future research topics.