Numerical Simulation Of The Thermo-mechanical Coupling Effects In Discontinuous Reinforced Metal Matrix Composites

Discontinuous reinforced metal matrix composites have high material performances,such as high specific strength and specific modulus, good thermal conductivity and electricalconductivity, lower thermal expansion coefficient, and better wear resistance property and soon, with a broad application prospect in the high-tech industry and national defense industry.Moreover, compared with continuous fiber reinforced metal matrix composites, this kind ofcomposites have some unique advantages such as the simpler preparation technology, lowerequipment requirements and cost ect. They are convenient for mass production and hasbecome one of the main direction of the metal matrix composites development.Based on the theory of continuum mechanics, the association was researched betweenthe material mesoscopic structure and the macroscopically overall thermal elastic properties,as well as the mechanical behavior of materials under thermal and mechanical load, so as toprovide the theoretical guidance for predicting the overall properties in the process ofdeveloping the materials and the practical application.The Unit Cell Model was employed that can reflect the mesoscopic structurecharacteristics of the discontinuous reinforced metal matrix composites. Two kinds of thehomogenization methods, namely direct homogenization method and the two-scaleasymptotic homogenization method, were realized by means of finite element method, whichwere applied to analyze the materials macroscopic performance. Then the Unit Cell FEMModel including the hexahedron with spherical inclusion or cylindrical inclusion was use tomodel the particle-reinforced materials or the short fiber-reinforced materials respectively,which was applied in the periodic boundary condition. For the direct homogenization method,this model could be loaded with uniform stress. For the two-scale asymptotic homogenizationmethod, this model should be loaded with thermal stress method according the formulation ofFEM according to the characteristic equation in the Unit Cell domain. According to the datacharacteristics of the results of the analysis with ABAQUS and Gauss integral theory, theMatlab program is coded to realize the volume integral of the field variables in the Unit Celldomain.By the previous two homogenization theory to analyze two kinds of Unite Cell modelwith two kinds of inclusion, according to the results of the analysis, the effective modulus ofthe model with cylinder inclusion was bigger than the one of the model with sphericalinclusion and the coefficient of thermal expansion (CTE) was lower, so the reinforcementeffect was better. But this model resulted into high stress concentration. At the same time, the effective modulus of the composites got higher and its coefficient of thermal expansion (CTE)got lower with the increase of the volume fraction of reinforcement. In addition, the effectivemodulus of the composites increased, the deformation of the Unit Cell and the maximumstress and strain which represented the meso-field in the material decreased gradually. In thethermal-mechanical coupling analysis, the effective modulus decreased with the increase ofthe temperature. The characteristic displacement and the maximum strain in the mesostructureincreased significantly with the increase of temperature, but the maximum stress increasedinitially then decreased. It found that the reinforcement could hinder the material thermalexpansion behavior and the expansion of matrix could aggravate the stress concentration. Atlast, in the use of the preparation of composites, the relative thermal elastic performance wastested. The result of tests had the same variation trend with the numerical result. It show thatthe bigger the volume fraction of the reinforcement, the bigger the elasticity modulus, but thesmaller the CTE. Althouhg there were some difference between the experiment data and thecalculated value, the result was still acceptable within the limit of error.