Abstract

Elastomers consist of long polymer chains joined together by chemical bonds through cross-linkers. They are usually capable of recovering their original shapes after finite deformation due to covalent cross-linkages. During a loading-unloading process, energy dissipates due to friction between polymer chains and the elastomer exhibits viscoelastic behavior. Mathematically, the viscoelasticity of elastomers has been decomposed into hyperelastic and viscous parts, which are attributed to the nonlinear deformation of the cross-linked polymer network and the diffusion of free chains, respectively. The hyperelastic deformation of a cross-linked polymer network is governed by the cross-linking density, the molecular weight of the polymer strands between cross-linkages, and the amount of entanglements between different chains, which we observe through large scale molecular dynamics (MD) simulations. The energy dissipation during a loading and unloading process of elastomers is governed by the diffusion of free chains, which can be understood through their reptation dynamics. Combing the non-affine network model for hyperelasticity and modified tube model for viscosity, we have developed a physics-based constitutive model for finite strain viscoelasticity of elastomers. All the parameters in the proposed constitutive model have physical meanings, which are signatures of polymer chemistry, physics or dynamics. Such a physics-based constitutive model can be used to understand the viscoelasticity of elastomers, and further applied to design elastomers with tailored properties.

Bio

Dr. Ying Li joined the University of Connecticut in 2015 as an Assistant Professor in the Department of Mechanical Engineering and Institute of Material Science. His current research interests are: multiscale modeling, computational materials design, and mechanics of soft matter. Dr. Li’s achievements in research have been widely recognized by fellowships and awards, such as Best Paper award from EMI Fluid Dynamics Technical Committee (FDTC) (2018). He has authored and co-authored more than 80 peer-reviewed articles, including Physical Review Letters, ACS Nano, Biomaterials, Nanoscale, Journal of Mechanics and Physics of Solids and Journal of Fluid Mechanics etc. He has been invited as reviewer for more than 60 international journals, such as Nature Communications, ACS Nano, Nanoscale. He currently serves as the Topic Editor of MDPI-Polymers, an international leading journal in polymer field.