CAREER: Fundamental Studies of Glassy Polymer Mechanics

非技术总结这个职业奖项支持计算和理论研究，以及玻璃聚合物力学领域的教育。了解聚合物材料(如结构塑料)的强度和失效具有重要的工业意义，这使得定量预测其整个力学响应范围成为物理聚合物科学的重要目标。聚合物材料是由具有重复的化学单元的长链分子组成的。化学上不同的聚合物表现出显著不同的机械性能；机械响应的巨大差异在决定这些材料的抗断裂稳定性方面起着重要作用。了解这些不同的力学响应对于开发新的高性能材料以及预测现有系统的故障行为和运行寿命至关重要，但在了解它们方面进展缓慢。解释观察到的各种行为仍然是一个悬而未决的问题，微观的、基于物理的模型到目前为止在预测水平上还不能令人满意。虽然计算机模拟可以提供关于模型系统变形过程中发生的现象的基本完整的信息，但在缺乏总体理论框架的情况下，对这些信息的物理解释可能很困难。最近开发的尚未通过模拟测试的候选框架为变革性进展提供了机会。这项研究涉及协调建模，它将利用这个机会和最近实验工作中出现的其他机会。该项目长期目标的进展将促进坚固、轻质结构塑料的开发，这些塑料可用于从汽车到武器的各种应用。该项目有助于培训两名学生学习聚合物物理、统计力学和计算机模拟，并有助于培养一支现代材料劳动力队伍。该奖项还有助于通过参与美国物理学会桥梁计划，增加未被充分代表的少数族裔学生，包括非裔美国人、西班牙裔美国人和美洲原住民，获得更高的物理学学位。PI计划承担当地桥牌学生招生、招生和指导的主要责任，以及教授科学技术工程和数学专业发展课程。PI还将继续制定招生的非认知标准，并努力确保在Bridge计划和当地的应用物理学博士计划中实施这些标准。技术总结这个职业奖项支持计算和理论研究，以及玻璃聚合物力学领域的教育。该项目包括一个模拟和分析建模计划，将显著增强对聚合物玻璃的机械性能如何与其微观相互作用和中尺度顺序相关的基本物理理解。模拟将通过改变局部链刚性、样品制备方案和变形历史(包括温度)，系统地将微观和细观结构的不同力学响应联系起来。系统将变形为断裂，以确定这些因素如何影响最终的力学性能，如延性和韧性。粗粒度方法的相对较低的计算成本将被用来探索远比化学细节模型可行的更广泛的相关参数空间。分析工作既是对模拟的补充，也是对最近发展的基于微物理的聚合物力学理论的扩展，通过一个迭代过程，模拟发现理论中的问题，根据需要改进理论，然后用于做出新的预测，这些预测将通过精心设计的后续模拟进行验证。这种结合的方法旨在最大限度地促进社区的长期目标，即获得足够的物理理解水平，以开发可预测的材料设计原则，以定制机械响应。该项目长期目标的进展将促进坚固、轻质结构塑料的开发，这些塑料可用于从汽车到武器的各种应用。该项目有助于培训两名学生学习聚合物物理、统计力学和计算机模拟，并有助于培养一支现代材料劳动力队伍。该奖项还有助于通过参与美国物理学会桥梁计划，增加未被充分代表的少数族裔学生，包括非裔美国人、西班牙裔美国人和美洲原住民，获得更高的物理学学位。PI计划承担当地桥牌学生招生、招生和指导的主要责任，以及教授科学技术工程和数学专业发展课程。PI还将继续开发非认知标准的招生和工作，以确保它们在桥梁计划和当地的应用物理学博士计划的实施。

NONTECHNICAL SUMMARYThis CAREER award supports computational and theoretical research, and education in the field of glassy polymer mechanics. The industrial importance of understanding strength and failure of polymeric materials, such as structural plastics, has made quantitatively predicting their entire range of mechanical response an important goal of physical polymer science. Polymeric materials are composed of long chain molecules with repeating chemical units. Chemically different polymers exhibit dramatically different mechanical properties; large differences in mechanical responses play a major role in determining the stability of these materials against fracture. Understanding these different mechanical responses is critical to developing new high-performance materials as well as predicting the failure behavior and operational lifetime of existing systems, yet progress towards understanding them has been slow. Explaining the variety of behaviors observed has remained an open problem and microscopic, physics-based models are so far unsatisfactory at a predictive level. While computer simulations can provide essentially complete information on phenomena occurring during deformation of model systems, physical interpretation of this information can be difficult in the absence of an overarching theoretical framework. Recently developed candidate frameworks that have not yet been tested by simulation provide an opportunity for transformative advance. The research involves coordinated modeling that will exploit this opportunity and other opportunities that have emerged from recent experimental work. Progress toward the long term goals of this project will facilitate development of strong, lightweight structural plastics that can be used in applications ranging from automobiles to armaments. This project contributes to training two students in polymer physics, statistical mechanics, and computer simulations and contributes to developing a modern materials workforce. This award also contributes to enhance access of underrepresented minority students, including African Americans, Hispanics, and Native Americans, to higher degrees in physics through participation in the American Physical Society Bridge Program. The PI plans to assume primary responsibility for local Bridge student recruitment, admissions, and mentoring, as well as teaching a Science and Technology Engineering and Mathematics Professional Development course. The PI will also continue developing non-cognitive criteria for admissions and work to ensure their implementation within the Bridge Program and the local Applied Physics PhD program.TECHNICAL SUMMARYThis CAREER award supports computational and theoretical research, and education in the field of glassy polymer mechanics. The project includes a program of simulations and analytical modeling that will significantly enhance basic physical understanding of how the mechanical properties of polymer glasses relate to their microscopic interactions and mesoscale order. Simulations will systematically relate differences in mechanical response to differences in micro- and meso-structure by varying local chain stiffness, sample preparation protocol, and deformation history, including temperature. Systems will be deformed to fracture in order to determine how these factors influence ultimate mechanical properties, such as ductility and toughness.The relatively low computational cost of the coarse-grained approach will be exploited to explore relevant parameter spaces far more broadly than is feasible for chemically detailed models. Analytical work will both complement the simulations and extend recently developed microphysics-based theories of polymer mechanics, through an iterative process wherein simulation uncovers problems with theories, the theories are improved as needed, and then used to make new predictions that will be tested by carefully designed follow-up simulations. This combined approach is designed to contribute maximally to the community's long term goal to obtain a level of physical understanding sufficient to develop predictive materials design principles to tailor mechanical response. Progress toward the long term goals of this project will facilitate development of strong, lightweight structural plastics that can be used in applications ranging from automobiles to armaments. This project contributes to training two students in polymer physics, statistical mechanics, and computer simulations and contributes to developing a modern materials workforce. This award also contributes to enhance access of underrepresented minority students, including African Americans, Hispanics, and Native Americans, to higher degrees in physics through participation in the American Physical Society Bridge Program. The PI plans to assume primary responsibility for local Bridge student recruitment, admissions, and mentoring, as well as teaching a Science and Technology Engineering and Mathematics Professional Development course. The PI will also continue developing non-cognitive criteria for admissions and work to ensure their implementation within the Bridge Program and the local Applied Physics PhD program.