报告主题：Highly-stretchable Double-network Composite
Inspired by the toughening mechanism of double-network (DN) hydrogels, a soft composite consisting of fabric mesh and VHB tape layers was fabricated. The composite was as strong as the fabric mesh, and as stretchable as the VHB tape. At certain compositions, the composite was significantly stronger and tougher than the base material. The extensibility and toughens of the composite can be attributed to the damage delocalization mechanism similar to that of DN gels. 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, asimple1D model has been developed for the damage evolution process in the composite. The predictions of the model have achieved good agreements with the measured properties of the composite in various compositions. The composite itself may also be regarded as a macroscopic model for the study of DN gels.
Dr. Wei Hong is currently an Associate Professor of Aerospace Engineering at Iowa State University, where he also holds the courtesy appoints from the Departments of Materials Science and Engineering and Mechanical Engineering. Since June 2015, Dr. Hong has been jointly appoint by the Global Station for Soft Matter at Hokkaido University in Japan. Before joining Iowa State University in 2008, Dr. Hong was a Postdoc Research Fellow at Harvard University for two years. He got his Ph.D. in Engineering Sciences from the Division of Engineering and Applied Sciences at Harvard University in May 2006, and his B.S. and M.S. degrees from the Department of Engineering Mechanics at Tsinghua University in 2000 and 2002, respectively. Dr. Hong’s research interest lies in the broad area of mechanics of materials and structures. Currently, he is mostly interested in soft composite materials, polymers and polymeric gels, mechanical and electrical damages in materials, instability phenomena, and mechanics in electrochemical reactions.