Computational Micromechanical Analysis On The Mechanical Properties Of SiC/Al Composites

Strain gradient theories have been established to explain the size dependent effect.Huang et al.developed a conventional theory of mechanism-based strain gradient plasticity(CMSG),which is a low-order theory of CMSG.The major work of this dissertation is to investigate a series of problems with CMSG.1.Based on low-order theory of CMSG,we develop the four node quadrilateral element and ten node tetrahedron element subroutine to realize the constitutive equation of SiC/Al metal composite and verify the correctness of the subroutine.2.Particle cluster distribution often exists in particle reinforced composites.The influence of particle clustered distribution on macroscale response and microscale damage of Si C reinforced particles of Metal-Matrix Composite(MMC)is investigated through finite element method.The microstructure model of particle cluster distribution is generated by the random sequential adsorption algorithm.In order to eliminate the influence of the boundary of the model,the periodic boundary conditions are applied to the uniaxial tensile load.In the loading process,the constitutive relations of the UMAT subroutine and the damage criterion of USDFLD subroutine are used to define the plastic deformation of the matrix and the damage of the particles.This paper mainly studies the damage evolution process of the model of uniform particle size distribution and particle cluster distribution under uniaxial tension.And then the effects of particle size and particle size distribution on the damage evolution are analyzed.3.Metal matrix composites have the advantages of high rigidity and high strength,but also its mechanical behavior is more complex than single material.The stress concentration near the enhancement phase will lead to the damage of the material,such as fracture,debonding and damage.So the analysis on the interfacial strength is particularly important.A program is developed to generate automatically 2D micromechanical finite element models including interface,in which both the locations and dimensions of Silicon–Carbide particles are randomly distributed.Finite element simulations of the deformation and damage evolution of Si C/Al composite are carried out for different microstructures and interphase strengths under tensile,shear and combined tensile/shear loads.A series of computational experiments are performed to study the influence of particle volume fraction,interface strengths and loading conditions on composite stiffness and strength properties.