基于多层次结构的结晶聚合物纳米复合材料有效性能--体积分数和等效模量的关系研究

原位聚合法制备的尼龙6/纳米S iO2复合材料具有很好的综合力学性能。加入相当低的纳米颗粒体积分数,可使纳米复合材料性能明显提高,但在其体积分数超过某一较小的临界值后,继续增加纳米颗粒体积分数,不再有增强效果。这一实验发现与以往的细观力学预测不一致,一直没有合理的解释。本文从材料的微观结构特点出发,揭示了上述现象的微观物理机制,将结晶聚合物纳米复合材料内部结构分别用宏观、细观和纳观三个层次来描述。利用数学上的渐近均匀化理论,结合有限元方法,经四次纳观层次的均匀化和一次细观层次的均匀化,预测了聚合物纳米复合材料的有效性能,揭示了聚合物纳米复合材料有效模量随纳米颗粒体积分数增加出现先增大后减小的变化规律。

PREDICTION OF EFFECTIVE PROPERTIES OF CRYSTALLINE POLYMER NANOCOMPOSITES BASED ON MULTILEVEL STRUCTURE--THE RELATION BETWEEN VOLUME FRACTION AND EFFECTIVE MODULUS

Nylon 6/SiO_2 nanocomposite prepared by in-situ polymerization shows prominent mechanical properties.The properties of nanocomposite increase evidently when a little nanoparticle is appended.But after nanoparticle volume fraction exceeds to a critical value,the property has no improvement.The experiment result is different from micromechnics,however it has no reasonable explanation at all times.Based on the experiment analysis of crystalline polymer nanocomposites,internal structure of crystalline polymer nanocomposites was described by multilevels(macroscopic,microscopic and nanoscopic levels).The finite element method was combined with homogenization theory based on asymptotic expansion for predicting effective properties of crystalline polymer nanocomposites,four nanoscopic level homogenizations and one microscopic homogenization were used.The effective property of polymer nanocomposite was analyzed.The variation rule of effective modulus of polymer nanocomposite with nanoparticle volume fraction was uncovered.