【作者】 梁希；

【导师】 李慧剑；

【作者基本信息】 燕山大学 ， 工程力学， 2013， 博士

【摘要】 空心颗粒复合材料是一种具有轻质、高强、高吸能、多功能特性的复合材料，在工程实际中被广泛应用。对于空心颗粒复合材料，根据空心颗粒体积填充比的大小以及颗粒的分布状态，可将空心颗粒复合材料分为填充型和胶结型两种类型。针对这两种类型的空心颗粒复合材料，分别建立了各自的力学模型，并基于细观力学的分析方法分析了空心颗粒复合材料的宏细观力学性能。针对填充型空心颗粒复合材料，利用RSA（Random Sequential Adsortion）方法建立了不同特质参数下（主要指空心颗粒体积填充比和壁厚）的空心颗粒复合材料的周期性代表体积单元模型，通过合理设置空心颗粒及基体的材料属性以及边界条件，计算得出了不同特质参数下复合材料的本构关系。将材料的本构曲线拟合为双线性特征，得出了材料的有效弹性模量、泊松比、屈服极限以及热膨胀系数等弹性常数，并分析了各特质参数与材料的弹性常数之间的相互关系。将各特质参数与材料的弹性常数之间的相互关系拟合为指数函数，然后分析了各特质参数对材料力学性能影响的灵敏度，以此来评价材料的稳定性。通过实验结果与数值模拟结果的对比发现，材料内部的初始缺陷对计算结果影响很大。将初始缺陷以球形孔洞的形式加入到材料的代表体积单元模型中去，利用有限元分析了初始缺陷程度对材料各弹性常数的影响规律。通过与实验结果的对比分析估计出了实验中材料的缺陷程度。还将Differential scheme方法做了改进，将缺陷因素考虑到其中去，作为有限元计算结果的比照。将材料的缺陷程度与材料各弹性常数之间的相互关系拟合为指数函数，分析了缺陷程度对材料弹性模量及屈服极限影响的灵敏度。针对胶结型颗粒复合材料，提出了计算材料宏细观力学性能的组合球单元方法：将胶结型颗粒复合材料中的一对颗粒及其胶结基体视为一个组合球单元，分别得出了组合球单元在轴向、切向及其弯曲三个方向的刚度，利用直接法构建了组合球单元的单元刚度矩阵，并将材料细观结构等效为刚性梁-弹簧网络模型。以平面六边形排列方式组合的颗粒复合材料为例，计算得出了基体中的应力分布函数、三个方向的刚度，以及弹性常数和细观应力集中系数。最后，将组合球单元方法推广到胶结型空心颗粒复合材料中去。其中的关键步骤是当球壳顶部受法向集中载荷时，将球壳的受力变形区域简化成了扁壳；当球壳顶部受切向集中载荷时，将球壳的受力变形区域简化成了平面问题。通过计算空心颗粒组合球单元的各向刚度，将胶结型空心颗粒复合材料等效为刚性梁-弹簧网络模型，然后计算出材料的有效弹性性能，并制定组合球单元的失效准则，模拟材料损伤演化的过程。更多还原

【Abstract】 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.更多还原