Abstract Many experiments have apparently shown that hard nanoparticle-reinforced elastomer matrix composites have not only an improved loading bearing capacity but also a good flexibility. The microscopic damage mechanism and its effect on the mechanical properties of such composites are systematically investigated in this paper by both tensile and tear experiments on nano-silica-particle reinforced silicone rubber composites, in which not only the case of surface unmodified nano-silica particles but also that of surface modified nano-silica particles is considered. It is found that both the ultimate strength and toughness of both composites increase monotonically with an increasing weight fraction of nanoparticles. The improved strength and toughness of silicone rubber composites reinforced by surface unmodified nanoparticles are attributed to the blocking effect of micro-sized agglomerations on crack propagation and the weak interface debonding between agglomerations and matrix, respectively. As for the composites with surface modified nanoparticles, not only the filler-blocking effect but also the strong interface between fillers and matrix is responsible for the remarkable strengthening, while the improved toughness is attributed to the crack-pinning and interface debonding around fillers. Another interesting finding is that, with the increase of nanoparticle fractions, formation of the main crack in both composites is firstly inhibited by the filler-blocking effect, and then re-activated by micro-crack coalescences. As a result, the final fracture elongation changes from increase to decrease when the nanoparticle fraction is beyond a critical value. The results in the present paper disclose different microscopic mechanisms that influence the strength and toughness of silicone rubber-based composites reinforced by surface unmodified and modified nanoparticles, which is helpful not only for the understanding of mechanical performance of nanoparticle-reinforced flexible elastomer composites, but also for the design of novel flexible composites with matching strength and toughness.

中文翻译：

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微观结构损伤对二氧化硅纳米粒子增强硅橡胶复合材料力学性能的影响

摘要 许多实验表明，硬纳米颗粒增强弹性体基复合材料不仅具有提高的承载能力，而且具有良好的柔韧性。本文通过纳米二氧化硅颗粒增强硅橡胶复合材料的拉伸和撕裂实验系统地研究了微观损伤机制及其对此类复合材料力学性能的影响，其中不仅表面未改性纳米二氧化硅颗粒的情况但也考虑了表面改性的纳米二氧化硅颗粒。发现两种复合材料的极限强度和韧性都随着纳米颗粒重量分数的增加而单调增加。由表面未改性纳米粒子增强的硅橡胶复合材料的强度和韧性的提高分别归因于微米级团聚体对裂纹扩展的阻塞作用以及团聚体与基体之间的弱界面脱粘。对于具有表面改性纳米粒子的复合材料，不仅填料封闭效应而且填料与基体之间的强界面是显着增强的原因，而韧性的提高则归因于填料周围的裂纹钉扎和界面脱粘。另一个有趣的发现是，随着纳米颗粒比例的增加，两种复合材料中主裂纹的形成首先被填料阻塞效应抑制，然后被微裂纹聚结重新激活。因此，当纳米颗粒分数超过临界值时，最终断裂伸长率由增加变为减少。本文的结果揭示了影响表面未改性和改性纳米粒子增强硅橡胶基复合材料强度和韧性的不同微观机制，这不仅有助于理解纳米粒子增强柔性弹性体复合材料的力学性能，而且也用于设计具有匹配强度和韧性的新型柔性复合材料。