报告时间：10月14日(周一) 下午2:30-5:00
报告地点：我校 新主楼C706
报告人：Victor P.W. Shim
报告摘要：
Polymers are widely utilized, and with the development of nanotechnology, nano-sized fillers have been incorporated into them to enhance their mechanical properties (e.g. modulus, strength and failure strain). These polymer nanocomposites have potential for automobile and aerospace applications. In such applications, dynamic loads from accidental collision, foreign-object impact, etc, are commonly encountered. Hence, an understanding of the dynamic behavior of polymers and their nanocomposites is essential for effective usage. This study comprises two aspects. Firstly, two types of silica nano-particles with different surface modifications, are used to reinforce Nylon6. One results in uniform particle dispersion but weak bonding with Nylon6 molecular chains. The other yields strong covalent bonds between the nanoparticles and the matrix, but less uniform dispersion (particle agglomeration). Samples of the two types of nanocomposites are subjected to dynamic compression using a Split Hopkinson Bar, and the effects of strain rate, nano-particle quantity, particle dispersion and particle-matrix bonding on the resulting mechanical properties are examined. In the second part of this study, the influence of stress states on the failure of a polymer is examined, because in actual applications, polymer components and products experience complex modes of loading, involving compression/tension/shear. Hence, information on failure under only uniaxial loading is insufficient. Quasi-static and dynamic tension are applied to Nylon6 specimens of various geometries to achieve different stress states. The results show that for stress triaxialities (ratio of hydrostatic to equivalent stress) larger than 0, the failure strain of nylon6 first increases then decreases, with a peak value for a triaxiality of ~0.4.
报告人简介：
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