Effect of Bi-dispersing Silica Particles on Mechanical Properties of Epoxy Composites

实验研究了双分散球形二氧化硅颗粒对环氧复合材料力学性能的影响，并用颗粒分散模型进行了理论分析。本研究采用的试样材料为双酚a型环氧复合材料，由不同的球形二氧化硅颗粒增强；纳米二氧化硅颗粒直径为240 nm，微二氧化硅颗粒直径为1。直径56毫米。试样具有不同的粒度组成。我们测量了复合材料的力学性能，即热粘弹性和断裂韧性。玻璃态复合材料的粘弹性性能与颗粒大小无关，而与颗粒的总体积分数有关。在橡胶状态下，由于颗粒流动性的增加，其性能与颗粒大小有关。采用Bansal和Ardell统计方法对各复合材料随机分布颗粒之间的距离进行数值分析。随机分布粒子的最接近表面距离取决于粒子的体积分数，并与其直径成正比。。然后，基于颗粒体积分数相同的各复合材料颗粒分布相似，建立理论模型，考虑单颗粒分散复合材料断裂韧性的混合规律；我们发现复合材料的断裂韧性与(i)颗粒表面之间平均距离的平方根和（ii）由等效包含方法给出的矩阵中的归一化平均应力的乘积的倒数近似成线性关系。理论结果与实验结果吻合较好。然而，断裂韧性的混合规律中包含未知参数，预测该参数与聚合物基体中颗粒与交联结构的相互作用有关。因此，我们澄清了颗粒双分散复合材料在玻璃态下的热粘弹性性能仅由颗粒的总体积分数决定，而断裂韧性则由颗粒尺寸和体积分数的分布决定。基于这一结论，我们得出复合材料的热粘弹性和断裂性能可以独立定制。少

Effect of bi-dispersing spherical silica particles on mechanical properties of epoxy composites were investigated experimentally and also analyzed using model of particle dispersion theoretically. The materials of specimens used in this study were bisphenol A-type epoxy composites reinforced by different spherical silica particles; nano-silica particle with 240 nm in diameter and micro-silica particle with 1. 56 mm in diameter. The specimens had different particle size compositions. We measured mechanical properties, namely thermo-viscoelasticity and fracture toughness, of the composites. The viscoelastic properties of the composites in glassy state were independent of particle size and governed by total volume fraction of the particles. The properties in rubbery state were found to have dependency on particle size due to increasing particle mobility. Distance between randomly-distributed particles for each composite was analyzed numerically by Bansal and Ardell's statistics method. Th … More e nearest surface distance of randomly-distributed particles is dependent on the volume fraction of the particles and proportional to its diameter. Then, based on similar particle distribution for each composite having the same volume fraction of the particles, we constructed theoretical model and considered mixture law of fracture toughness for single-particle dispersed composite. We found that the fracture toughness of the composites was approximately linear with respect to the reciprocal of the product of (i) the square root of the mean distance between the particle surfaces, and (ii) the normalized mean stress in the matrix given by the equivalent inclusion method. The theoretical result agreed well with the experimental results. However the mixture law of fracture toughness included the unknown parameter which was predicted to be related to interaction between particle and cxosslink structure of polymer matrix. Therefore, we clarified that the thermo-viscoelastic properties of particles bi-dispersed composites in glassy state are determined only by total volume fraction of the particles and the fracture toughness are done by distribution of particle size and the volume fraction. Based on this conclusion, we obtained that thermo-viscoelastic and fracture properties of the composite can be tailored independently. Less