| The special superposition of the layered ceramics enables the researcher to proceed designing inside the layer and among layers from the macro-aspect to achieve new materials with superiority performace.The performance of the multilayer ceramic composites is affected by both the micro-polycrystalline structure and the macro-layered structure.However,in most simulation works,only the polycrystalline microstructure simulation of block ceramic materials is considered,lacking of the numerical simulation of “structure-mechanical response” relations of layered ceramic materials from the atomic scale,polycrystalline microstructure and layered structure and the related computing software.From the view of the micro-polycrystalline and macro-layered structure,the first principle method,the Monte Carlo(MC)method and the Finite Element method(FEM)are applied to analyze the mechanical response of layered ceramic composite with polycrystalline microstructure,and to develop a parameterized optimal design software for layered materials,providing guidance basis to the preparation of new type of layered ceramic matrix composites.The main research contents and research results are as follows:(1)The Monte Carlo method was applied to simulate the polycrystalline microstructure evolution,and the finite element method to analyze the mechanical response of polycrystalline microstructure.The mean grain size increases with the simulation time.The average stress and the grain size agree well with the Hall-Petch relationship.(2)On the basis of the polycrystalline microstructure evolution for a single layer,the Monte Carlo simulation was applied to simulate the microstructure evolution for a layered material,and the finite element analysis was preformed to investigate the mechanical response,which was mainly focused on the effects of the grain orientation,grain boundary properties,and the laminated topological structures such as number of layers,the layer thickness ratio and the modulus ratio.(a)For a three-layered material,when the layer thickness ratio changes,the proportion of material hard(soft)layer changes,and the average stress of the corresponding microstructure model changes,consequently.When the modulus ratio of the interlayer and the outlayer is larger than 2,the average stress increases with the thickness of interlayer,while the modulus ratio is less than 1,the average stress decreases with the thickness of the interlayer.(b)For a material with strengthing grain boundary,regardless of the stacking sequence of material(the outer layer is hard or soft),the average stress of layered material decreases with the simulation time.The average stress of the layered material with outer hard layer decreases with the number of layers,while average stress of the layered material with outer soft layer increases with the number of layers.(c)The average stress increases almost linearly with the modulus ratio for the homogeneous materials,whereas it is nonlinear for the heterogeneous polycrystalline layered materials.(3)The residual stress and the apparent fracture toughness of layered ceramic composites were calculated,and the effect of the material parameters such as the number of layers,the layer thickness ratio,the modulus ratio and other parameters on the residual stress and the apparent fracture toughness were discussed.(a)When the layer thickness ratio of the odd and the even layer equals to 1,the single layer become thinner when the number of layer increases,resulting in that the residual stress in compressive layers increses and that in tensile layer decreases.When the crack tip locates in the outer compressive layer,the apparent fracture toughness inreases with the number of layers.When the total thickness ratio of odd layers and the even layers equals to 1,the compressive and tensile stresses are with the same magnitude,which keeps unchanged whatever the number of layers is.The apparent fracture toughness at the interface of compressive/tensile layer decreases as the number of layers,while that at the interface of tensile/compressive layer increases as the number of layers.(b)The compressive residual stress decreased with the layer thickness ratio of the odd and the even layer,while the tensile residual stress increased with the layer thickness ratio of the odd and the even layer.The apparent fracture toughness in the compressive layer increases with the layer thickness ratio.(c)The higher sintering temperature results in the larger apparent fracture toughness at the compressive/tensile interface and the smaller apparent fracture toughness at the tensile/compressive interface.(d)The apparent fracture toughness decreases with the modulous ratio at the compressive/tensile interface,while it increases with the modulous ratio at the tensile/compressive interface.(4)A interactive graphical user interface software PCLab(Partical Cloud Laboratory)was developed based on the object-oriented program design under the OMTDesk software platform,providing multilayer polycrystalline microstructure evolution and mechanical response analysis with the MC and FEM software integration modules.It can quickly and effectively investigate the mechanical properties of the layered material to solve multiple physical field problems.(5)A macro and micro design idea was proposed for layered composites coupled with the First principle method,Monte Carlo simulation and Finite Element simulation,and the numerical simulation of the relationship between the structure and mechanical response of the so-designed HfC/BN,Zr B2/BN and SiC/BN three-layered materials was carried out from the atomic scale,polycrystalline microstructure and layered structure.The research results show that for the same polycrystalline structure and the grain interface effect,HfC/BN layered material has the strongest carrying capacity,ZrB2/BN comes second,and Si C/BN is the weakest;three kinds of layered materials can reach the same or similar mechanical response with different polycrystalline structures or different grain bouondary effects. |
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