CAREER: Glass/Polymeric Material Systems in Civil Infrastructure

玻璃窗对建筑物居住者的生活质量很重要，但当爆炸载荷将窗户震碎时，窗户可能会对居住者构成危险。这是一个对建筑物安全越来越重要的问题。此外，玻璃由于其独特的美学吸引力，在窗户以外的环境中是一种有吸引力的结构材料。该研究项目涉及开发无机(硅酸盐)和有机(聚合物)玻璃的破裂和损坏的创新模型，以及由交替的玻璃和弹性体层组成的夹层窗户。主要关注的是速率相关性和碎片大小和速度的准确预测。这些模型还将考虑框架和安装系统以及实际负载等实际问题。需要解决的主要科学障碍是更好的率相关粘弹性和塑性模型，更有效和更准确地使用内聚界面模型来显式模拟动态裂纹扩展，以及新的均匀化程序，该程序将在更粗的、计算上更可行的网格上捕获非常精细的内聚有限元模拟的结果。这些障碍中的每一个都提出了有趣的技术问题；例如，在内聚界面模型的情况下，即使是元素大小的有效范围这一基本问题目前也不完全理解，将在本研究工作中加以阐明。研究中的一个重要主题是跨越不同的时间尺度：所考虑的最快现象，即动态裂纹通过一个过程区长度的扩展，发生在比表面损伤积累所需的间隔短约18个数量级的间隔内。因此，将特别关注能够对许多不同时间尺度和频率做出准确预测的模型，以及可以省去非常小步骤的均化技术。拟议职业计划的教育方面涉及为本科生培养工业经验，重组本科生和研究生课程，以包括更现代的材料强度，特别是非弹性材料的强度，创建一门新的本科高级结构系统课程，涵盖非线性材料建模，以及创建与拟议研究直接联系的计算固体力学研究生研讨会。对于这些课程中的大多数，将开发基于工业实践的新案例研究，以及为课堂使用量身定做的新计算机代码。拟议研究计划的成果包括能够更有效地预测安全建筑中窗户的安全性的计算模型和方法，更好地评估自然发生的荷载(如阵风和小颗粒破坏)下的耐久性的模型，以及对断裂力学和加载率影响的新见解。教育计划的成果将是让学生更好地了解不同长度和时间尺度的材料(特别是非弹性材料和非线性材料)建模的目的和方法，新的面向教育的可用于各种课堂环境的有限元代码，以及面向K-12学生的新的教学模块。

Glass windows are important for quality of life of a building's occupants, but windows can pose a hazard for the occupants when a blast load shatters them. This is a matter of increasing significance for building security. In addition, glass is an attractive structural material in settings other than windows because of its unique aesthetic appeal. This research project deals with the development of innovative models for fracture and damage to inorganic (silicate) and organic(Polymeric) glass, and to laminated windows composed of alternating layers of glass and elastomer. Chief concerns are rate dependence and accurate prediction of fragment size and velocity. The models will also account for practical issues like framing and mounting systems and realistic loads. The main scientific hurdles to be resolved are better models for rate-dependent viscoelasticity and plasticity, more efficient and accurate use of cohesive interface models for explicit modeling of dynamic crack growth, and new homogenization procedures that will capture the results of a very fine-grid cohesive finite element simulation on a coarser more computationally feasible mesh. Each of these hurdles poses interesting technical questions; for example, in the case of cohesive interface models, even the basic matter of valid ranges for the size of the elements is currently incompletely understood and will be elucidated in this research effort. The computational models will be verified using laboratory experiments by industrial and academic collaborators.An important theme in the research is bridging the various time scales: the fastest phenomenonunder consideration, namely the propagation of a dynamic cracks through one process-zone length, takes place over an interval that is about 18 orders of magnitude shorter than the interval required for surface damage to accumulate. Therefore, special attention will be paid to models that are able to make accurate predictions for many different time-scales and frequencies, and to homogenization techniques that can obviate the need for very small steps.The educational aspect of the proposed CAREER plan involves the development of industrialexperience for undergraduates, restructuring of an undergraduate and graduate course to include more modern coverage of strength of materials especially inelasticity, creation of a new undergraduate course on advanced structural systems to cover nonlinear material modeling, and creation of a graduate seminar on computational solid mechanics with direct links to the proposed research. For most of these courses, new case studies based on industrial practice and also new computer codes tailored for classroom use will be developed. Outcomes of the proposed research plan include computational models and methods better able to efficiently predict the safety of windows in a secure building, better models for assessing durability under naturally occurring loads like wind gusts and damage from small particles, and new insight into fracture mechanics and the effect of loading rate. Outcomes of tthe educational plan will be students with a better appreciation for the purposes and methods of modeling of materials (particularly inelastic and nonlinear) at different length and time scales, new educationally oriented finite element codes useful in a variety of classroom settings, and new instructional modules for outreach to K-12 students.