Establishment On Numerical Simulation Countermeasures To Mechanical Properties Of The Hollow Particulate Composite

Hollow particulate composites is a kind of composite with light weight, high strength,high energy absorption capacity and multifunction characteristic, and is widely used inengineering practice. According to the volume fraction and the distribution state of thehollow particle, the composites is divided into two types: one type is called hollowparticle filled composite(with low volume fraction); another one is called cementedhollow particulate composite(with high volume fraction). The simulation calculationmodel which aim at the characters of each type of composite is established, respectively.At last, the mechanical property of the composite can be obtained based on themesoscopic mechanics analysis method.For the hollow particle filled composite, RSA (Random Sequential Adsorption)method was adopted to generate the periodic representative volume element models whichcontain the special parameters such as the volume fraction and the wall-thickness of thehollow particle. The reasonable material attributes and boundary conditions are set inorder to obtaining the constitutive relation of the composite material with different specialparameters. Material properties of the composite were simplified to bilinear kinematichardening model, and then the effective elasticity modulus, Poisson’s ratio, yield strengthand coefficient of thermal expansion are obtained. The relationships of the specialparameters and these elastic constants are analyzed. The relationships are fitted toexponential function respectively, with the purpose of analyzing the sensitivity of theinfluence of the special parameters to the elastic constants. The stability of the compositemechanical properties can be represented.Experimental results are compared with the numerical results. It shows that thereexisted a huge error. The reason of the error is the initial defect causing a great influenceto the mechanical properties of the composite. In order to improve the numerical method,the initial defects are considered into the model in the form of spherical voids. Theinfluence rules of the defect degree to the elastic constants of composite can be obtainedthrough the FEM analysis. The defect degree of the experimental material specimen can be estimate also. Differential scheme is also improved by considering the initial defect. Atlast, the relationships of the defect degree and the elastic constants are fitted to exponentialfunction respectively to analyze the sensitivity of the defect degree influence to the elasticconstants.For the cemented particulate composite, combinational sphere element method isintroduce to solve its mechanical problem. A pair of particles and the cement separatedfrom the composite constitute a combinational sphere element. The stiffness of acombinational sphere element on axial direction, tangential direction and bendingdirection are derived based on the elastic theory. The element stiffness matrix ofcombinational sphere element is obtained through the direct method. According to theelement stiffness matrix, the combinational sphere element can be described by anequivalent rigid beam-spring combinational model, so the composite can be described byan equivalent rigid beam-spring lattice. Finally, an example is taken out to show theapplication of the new method. Stress distribution function, stiffness on three directionsand macro effective elastic constants of composite are obtained.Finally, the combinational sphere element method is extended into the cementedhollow particulate composite. The critical process is how to simplify the spherical shell. Ifthe shell loads a normal concentrated force, the shell can be simplified to a shallowspherical shell; if the load is a tangential concentrated force, the shell can be simplified toa flat plate. And the stiffness of a combinational hollow sphere element on the threedirections can be obtained. The cemented hollow particulate composite can be alsodescribed by an equivalent rigid beam-spring lattice model. At last, the elastic propertycan be obtained. According to the failure criterion of the combinational sphere elementmethod established, the damage evolution of the material is described.