Modeling Of Interfacial Debonding And Characterization Of Thermo-mechanical Fatigue In Particle Reinforced Composites

With the development of science and technology, composite materials, for their attractive behaviors, have been utilized more and more widely in many important industries, such as aerospace, automobile, military production, nuclear energy, electronic industry and so on. For particulate reinforced composites, the material properties, both mechanical and thermal, can be improved by the particulate inclusions. On the other hand, the strength of fracture and fatigue will be decreased at the same time. Both the positive and negative effects depend on the size, shape, properties, and spatial distribution of those second phase inclusions. Simulation of the behaviors of such composites, influenced by numerous microstructures, is one of the significant topics in the field of mechanics and material science. This dissertation deals with the two-dimensional simulation of particulate reinforced composites using Voronoi Cell Finite Element Method (VCFEM). The main contributions can be listed as follows:1. Based on VCFEM, a scheme to describe the matrix-inclusion interfacial damage of particulate reinforced composites is proposed by establishing the functional, which is suitable to formulate both the traction reciprocity conditions on the undebonded inclusion-matrix interfaces and the traction free conditions along the debonded interfaces. Some improvement of VCFEM are proposed, such as, selection of appropriate stress functions, appropriate division of integral domains and derivation of analytic solution of line integral.2. A remeshing algorithm is proposed for the simulation of progressive matrix-inclusion debonding in particulate reinforced composites. The accuracy and efficiency of proposed methods are verified by comparison with the general nonlinear finite element codes MARC and ABAQUS. At the same accuracy, the present methods have the advantage of mechanics computation of heterogeneous materials that element meshing is simpler and computation is faster for real particulate reinforced composites, in which multiple inclusions are randomly distributed.3. A Voronoi cell element, formulated with creep, thermal and plastic strain, and interfacial crack, is proposed for the simulation of thermo-mechanical fatigue behavior of particulate reinforced composites. The influence of the relative phases ofmechanical fatigue and thermal fatigue loading on the thermo-mechanical fatigue hysteresis loop, and the influence of the topological micro-structure of inclusions on the thermo-mechanical fatigue behavior have been analyzed. Some valuable conclusions of thermo-mechanical behavior of particulate reinforced composites with complicated microstructures were obtained.In this dissertation, with proposed methods, mechanical behaviors and interfacial damage of particulate reinforced composites under both thermal loadings and mechanical loadings have been studied. It is valuable for the development of fatigue life prediction methods that the analysis method of interfacial damage under static loads is proposed and the influence of many factors on thermo-mechanical behaviors is obtained.