Collaborative Research: Nonlinear Mechanical Spectroscopy of Glassy Polymers to Probe Viscoelastic Constitutive Behavior

合作研究：玻璃态聚合物的非线性机械光谱学探测粘弹性本构行为

基本信息

批准号：
1662474
负责人：
Gregory McKenna
金额：
$ 21.14万
依托单位：
Texas Tech University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-06-01 至 2021-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1662474&HistoricalAwards=false
关键词：
Collaborative Research Nonlinear Mechanical Spectroscopy

项目摘要

This award supports research to characterize the nonlinear viscoelastic behavior of glassy polymers. Understanding the long-term mechanical behavior of glassy polymers is critical for assurance of the durability of glassy polymers in their use as stand-alone materials, or as matrix materials for advanced composites, in applications that require low-density and high specific strength materials, such as in automotive, sports, and aerospace industries. This project will take steps to address the challenge from a fundamental perspective using a novel nonlinear fingerprinting methodology that promises to bring important advances for development of premier products, hence benefiting US industry and society. In the past, the fingerprinting methodology has been used to characterize polymeric fluids. This award extends the method to polymer glasses, both through novel experiments and through appropriate nonlinear constitutive modeling and validation. The graduate students on the project will be trained in this cutting edge research, which involves experimental and computational mechanics of time-dependent materials, glassy polymer physics, and structure-property relations for engineering polymers. The project will also leverage STEM outreach programs at both Texas Tech University and University of Texas Dallas to excite K-12 students about science and engineering.Fundamental knowledge related to the nonlinear viscoelastic behavior of solid polymers will be pursued in this project. This requires a general scheme to classify the variety of observed behaviors and use these observations to challenge the relevant constitutive equations. The research will use the combined Large Amplitude Oscillatory Shear and Mechanical Spectral Hole Burning fingerprinting methodology to provide fingerprints of the nonlinear viscoelastic behavior of a series of glassy polymers and to challenge them against a set of nonlinear constitutive law predictions from several leading models from the literature. Not only will the work show that the method can be applied to glassy polymers, but by choosing to examine polymers with different degrees of heterogeneity, as estimated by the strength of the beta-relaxation, the method can differentiate among different types of nonlinear behavior and, in principle, determine how the details of the dynamic heterogeneity impacts the fingerprints and the constitutive model parameters. This provides an important advance in ideas of structure-property relations in the nonlinear mechanics of polymers. Furthermore, the work provides a critical evaluation of the fingerprinting paradigm, currently developed for shearing deformations in nonlinear fluids, by making measurements in non-volume preserving conditions, viz., tension and compression to develop material fingerprints as a function of said deformation geometries and comparing them to the shearing results.

该奖项支持研究表征玻璃状聚合物的非线性粘弹性行为。了解玻璃状聚合物的长期机械行为对于确保玻璃状聚合物用作独立材料的耐用性至关重要例如在汽车，体育和航空航天行业。该项目将采取步骤从基本的角度解决挑战，使用一种新颖的非线性指纹方法，该方法有望为开发主要产品的发展带来重要的进步，从而使美国的行业和社会受益。过去，指纹方法已用于表征聚合物流体。该奖项通过新型实验以及通过适当的非线性组成型建模和验证将方法扩展到聚合物眼镜。该项目的研究生将接受此尖端研究的培训，该研究涉及时间依赖的材料，玻璃状聚合物物理学以及用于工程聚合物的结构 - 毛皮关系的实验和计算力学。该项目还将利用德克萨斯理工大学和德克萨斯大学达拉斯大学的STEM外展计划，以激发K-12学生有关科学和工程学的知识。该项目将在该项目中追求与固体聚合物非线性粘弹性行为相关的基础知识。这需要一般方案来对观察到的各种行为进行分类，并使用这些观察结果来挑战相关的本构方程。该研究将使用合并的大振幅振荡剪切和机械光谱孔燃烧指纹方法来提供一系列玻璃状聚合物的非线性粘弹性行为的指标。这项工作不仅可以表明该方法可以应用于玻璃状聚合物，而且通过选择检查不同程度异质性的聚合物，如β-释放的强度所估计，该方法可以区分不同类型的非线性行为和不同类型，原则上，确定动态异质性的细节如何影响指纹和本构模型参数。这为聚合物的非线性力学中的结构特性关系的思想提供了重要的进步。此外，这项工作提供了目前针对非线性流体剪切变形而开发的指纹范式的批判性评估，通过在非数量保留条件下进行测量，即张力和压缩，即在上述变形的差距和构图中开发材料指纹，以开发材料指纹。将它们与剪切结果进行比较。