Collaborative Research: New Approaches to Predicting Long-time Behavior of Polymer Glasses

合作研究：预测聚合物玻璃长期行为的新方法

• 批准号: 2330760
• 负责人: Mehrdad Negahban
• 金额: $ 22.53万
• 依托单位: University of Nebraska-Lincoln
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2330760&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Approaches; Predicting

Glasses are non-equilibrium materials and their properties vary with time, thermal history, and mechanical deformation. A major impediment to the insertion of polymeric glasses in applications ranging from dielectric thin films in electronics to structural composites for aerospace, automotive, and wind turbine applications is the inability to predict long-term performance. This lack of quantitative understanding of the mechanical and thermal behavior also adversely impacts the application and engineering of amorphous glassy polymeric materials. This award supports research to facilitate the prediction of long-term behavior of polymer glasses, and thus facilitate the design and engineering of this important class of materials in advanced composites and other applications of importance to national interests. In addition, graduate and undergraduate students will be trained in polymer physics and mechanics, modeling, and experimental methods related to polymer glasses. At North Carolina State University, outreach will be conducted with K-12 summer camps to promote interest in STEM through a curriculum that includes teamwork, creative problem solving, and design challenges. Outreach activites at University of Nebraska Lincoln will focus on lifelong learner adults interested in expanding their understanding of math, physics, and programing.The Back Stress Expansion model will be investigated in order to develop a robust, yet computationally simplified, methodology that is able to describe and predict the long-term performance of glassy polymers as a function of thermal and mechanical history, including nonlinear or large deformations. In order to obtain a quantitatively correct description of material behavior, the model will be extended by incorporating i) a distribution of relaxation times, ii) the transition from the super-Arrhenius temperature dependence of the relaxation times above the glass transition to a weaker temperature dependence in the glassy state, and iii) the full multi-dimensional framework to model non-isotropic deformations. The model will be tested and validated using new experimental data, including pressure dependent structural recovery, isochoric measurements in the glassy state, and non-linear viscoelastic measurements. These experiments, which will be performed on three important engineering thermoplastics - polycarbonate, polysulfone, poly(methyl methacrylate) - will not only provide new data to validate and refine the model but will also further our understanding of the physics and mechanics of glassy polymers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

玻璃是非平衡材料，其性质随时间、热历史和机械变形而变化。聚合物玻璃在从电子介电薄膜到航空航天、汽车和风力涡轮机应用的结构复合材料等应用中插入的一个主要障碍是无法预测长期性能。这种对机械和热行为缺乏定量了解的情况也对非晶态玻璃聚合物材料的应用和工程产生了不利影响。该奖项支持有助于预测聚合物玻璃长期行为的研究，从而促进这一重要类别材料在先进复合材料和其他对国家利益具有重要意义的应用中的设计和工程。此外，研究生和本科生将接受与聚合物玻璃相关的聚合物物理和力学、建模和实验方法方面的培训。在北卡罗来纳州立大学，将与K-12夏令营一起开展外联活动，通过包括团队合作、创造性解决问题和设计挑战的课程来提高人们对STEM的兴趣。内布拉斯加州大学林肯分校的推广活动将集中在对扩展他们对数学、物理和编程的理解感兴趣的终身学习者成年人。将研究背应力扩展模型，以开发一种稳健的、但在计算上简化的方法，该方法能够描述和预测玻璃聚合物作为热和机械历史的函数的长期性能，包括非线性或大变形。为了在定量上正确地描述材料的行为，模型将被扩展，包括：i)弛豫时间的分布，ii)从玻璃态上的弛豫时间的超阿累尼乌斯温度依赖关系转变到玻璃态下较弱的温度依赖关系，以及iii)完整的多维框架来模拟各向同性变形。该模型将使用新的实验数据进行测试和验证，包括压力依赖的结构恢复、玻璃态下的等容测量和非线性粘弹性测量。这些实验将在三种重要的工程热塑性塑料-聚碳酸酯、聚砜、聚甲基丙烯酸甲酯-上进行，不仅将提供新的数据来验证和完善模型，还将进一步加深我们对玻璃聚合物的物理和力学的理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。