Soft but Tough – from Hydrogels to Kirigami
讲座名称：
Soft but Tough – from Hydrogels to Kirigami
讲座时间：
2017-03-14
讲座人：
洪伟
形式：
校区：
兴庆校区
实践学分：
讲座内容：
报告题目：Soft but Tough – from Hydrogels to Kirigami
报告时间：3月14日（周二） 下午：4:10
报告地点：航天学院第三会议室
报告人：Wei Hong (洪伟)
Department of Aerospace Engineering, Iowa State University, USA
Global Institution for Collaborative Research and Education, Hokkaido University, Japan
Abstract
This research seeksa pathway towards the structural design of materials that are soft but tough. Starting from the ultra-tough double-network (DN) hydrogels, the applicability of similar toughening mechanisms in other material systems or at a different length scale is investigated. A soft composite consisting of fabric mesh and VHB tape layers was fabricated, and was found to be as strong as the fabric mesh, and as stretchable as the VHB tape. At certain compositions, it was much tougher than either of the base materials. The extensibility and toughness of the composite can be attributed to the damage delocalization mechanism similar to that of DN gels, but at a much larger scale. In the partially damaged phase, the fabric mesh fragmented into small islands, surrounded by the highly stretched VHB tapes. The large non-affine deformation was accommodated by the finite sliding at the interface. Just as the DN gels, the coexistence of the partially damaged phase and intact phase resulted in a stable necking in the composite when subject to uniaxial tension. The propagation of the necking zone corresponded to a plateau on the stress-stretch curve. Irrecoverable hysteresis similar as in a DN gel were also observed during cyclic loading. To rationalize the observations and to better understand the physical mechanism, a simple model has been developed for the damage evolution process in the composite. The predictions of the model agree well with the measured properties at various compositions. In addition to the DN gels and composite, some other toughening mechanisms of soft materials are also explored. A more general guideline for designing materials and structures that are highly stretchable and extremely tough is proposed.
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