Shockwave Propagation and Dynamic Fracture of Hydrogels via Integrated Computational and Experimental Studies

该奖项支持研究水凝胶高变形率行为的实验和计算研究。水凝胶由吸附在水中的聚合物网络组成。水凝胶是一类重要的材料，因为它们的性质可以定制以模拟许多生物组织的行为。因此，水凝胶通常被用作皮肤、肌肉和人体器官(肺、心、脑等)的组织模拟剂。在研究创伤损伤的实验中。以前的大多数研究都集中在水凝胶在低变形速率下的行为。不幸的是，这些实验不能模拟高速变形引起的组织损伤(例如，突然坠落、滑雪损伤、车祸)和冲击波传播的影响(对肺、组织和大脑的非接触性爆炸损伤)。这项研究的结果将为更好地了解冲击波在生物组织中的传播和相关损害提供必要的知识。因此，这项研究将使退伍军人和其他患有创伤性软组织损伤的公民受益。此外，劳动力发展活动将有助于对研究生和本科生进行实验和模拟技术培训。这项研究将有助于理解与水凝胶动态行为有关的基本物理机制，例如波速随传播距离和水体积分数的变化。此外，这项研究将首次了解水凝胶中的高速粘度随水含量、高速剪切变形过程中的原子尺度应力和应变以及水凝胶样品中裂纹扩展速度的变化而变化。实验将使用一种独特的聚合物分离式霍普金森压杆进行，该压杆是为研究水凝胶材料中的冲击波传播和动态破裂而定制的。分子动力学模拟将被用来研究具有原子分辨率的冲击波的传播和粘度。结合实验和模拟的数据，将改进水凝胶动态力学行为的超弹性本构模型。水凝胶的高应变率粘度的实验测量和模拟将被用来发展新的速率相关的内聚区模型，用于预测水凝胶中的裂纹扩展。

This award supports experimental and computational research to study the high deformation rate behavior of hydrogels. Hydrogels consist of a polymer network absorbed in water. Hydrogels are an important class of materials because their properties may be customized to mimic the behavior of many biological tissues. Accordingly, hydrogels are commonly used as tissue simulants for skin, muscles and human organs (lungs, heart, brain, etc.) in experiments to study traumatic injuries. Most prior research has focused on the behavior of hydrogels at low deformation rates. Unfortunately, such experiments do not mimic the conditions associated with tissue injuries caused by high rate deformation (e.g., sudden falls, skiing injuries, automobile accidents) and the effects of shockwave propagation (non-contact blast injuries to lungs, tissue and brain). The results of this research will provide the knowledge necessary to better understand shockwave propagation and related damage in biological tissues. Thus, this research will benefit military veterans and other citizens with traumatic soft tissue injuries. Furthermore, workforce development activities will contribute to the training of graduate and undergraduate students in experimental and simulation techniques. This research will provide an understanding of the fundamental physical mechanisms related to the dynamic behavior of hydrogels, such as variation in wave velocity as a function of propagation distance and water volume fraction. Further, this research will provide a first understanding of high rate viscosity in hydrogels as a function of water content, atomic scale stresses and strains during high rate shearing deformation, and the rate of crack growth in hydrogel samples. Experiments will be conducted using a unique polymer split Hopkinson pressure bar customized to study shockwave propagation and dynamic fracture in hydrogel materials. Molecular dynamics simulations will be conducted to study shockwave propagation and viscosity with atomic resolution. Combined, data from experiments and simulation will be used to improve hyperelastic constitutive models for the dynamic mechanical behavior of hydrogels. Experimental measurement and simulation of the high strain rate viscosity of hydrogels will be used to develop novel rate dependent cohesive zone models for predictive simulation of crack propagation in hydrogels.