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: 2330759
• 负责人: Gregory McKenna
• 金额: $ 37.23万
• 依托单位: North Carolina State University
• 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=2330759&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。在从电子器件中的介电薄膜到用于航空航天、汽车和风力涡轮机应用的结构复合材料的应用中插入聚合物玻璃的主要障碍是不能预测长期性能。这种对机械和热行为的定量理解的缺乏也不利地影响了无定形玻璃态聚合物材料的应用和工程。该奖项支持促进聚合物玻璃长期行为预测的研究，从而促进先进复合材料和其他对国家利益具有重要意义的应用中这一重要类别材料的设计和工程。 此外，研究生和本科生将接受聚合物物理和力学，建模和与聚合物玻璃相关的实验方法的培训。 在北卡罗来纳州州立大学，将与K-12夏令营进行外展，通过包括团队合作、创造性解决问题和设计挑战在内的课程，促进对STEM的兴趣。内布拉斯加大学林肯分校的外展活动将侧重于有兴趣扩展他们对数学、物理和编程的理解的终身学习者成年人。将研究背应力膨胀模型，以开发一种稳健的、但计算简化的方法，该方法能够描述和预测玻璃状聚合物作为热历史和机械历史的函数的长期性能，包括非线性或大变形。 为了获得材料行为的定量正确描述，该模型将通过以下方式进行扩展：i）弛豫时间的分布，ii）从玻璃化转变以上的弛豫时间的超阿耳忒修斯温度依赖性到玻璃态中较弱的温度依赖性的转变，以及iii）完整的多维框架以模拟非各向同性变形。 该模型将使用新的实验数据进行测试和验证，包括压力相关的结构恢复，在玻璃态等容测量，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）-不仅将提供新的数据来验证和完善模型，而且还将进一步加深我们对玻璃态聚合物的物理和力学的理解。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。