CAREER: Constrained Slip, Cracking and Instability in Extremely Anisotropic Nanolayered Solids

该学院早期职业发展（CAREER）资助将专注于量化微观结构变形机制对具有纳米晶体结构的材料（如锌，云母和某些碳化物）的机械响应的影响。这些材料为在极端环境下（如高温下）需要可靠性能的技术带来了巨大的希望。然而，它们在关键应用中的使用受到严重限制，因为它们表现出极其依赖于方向（各向异性）的行为，不能适应任意形状的变化，并且本质上是脆性的。另一方面，这些材料的各向异性使它们能够通过晶体滑移、开裂和/或在较小尺度下的不稳定性经历宏观尺度变形，这反过来可以显著提高它们的损伤容限和延展性。该研究项目将提供对纳米层状晶体材料基于微结构的机械响应的基本理解，为微结构工程利用其损伤容限和延展性的应用奠定基础。这一目标将实现与综合实验计算的方法，这将导致在几个长度尺度的预测建模框架和实验数据。研究活动将辅之以一系列全面综合的教育和外联活动。教育活动将通过开发交互式教学材料和新课程来加强本科生和研究生水平的工程教育。外展活动将通过让德克萨斯州的高中教师参与研究和学生参加夏令营来提高对工程的认识。首先，通过新的小规模原位实验，了解晶体滑移，开裂和极各向异性纳米材料，氧化物，碳化物和氮化物的不稳定性的协同效应。其次，开发和验证基于晶体塑性的本构模型，将非Schmid效应，解理样开裂，和局部不稳定性预测这些材料的微观结构敏感的机械响应。这将为以下关键的基本问题提供答案：（i）什么材料属性或属性的组合影响单晶中滑移、开裂和不稳定性的发生和传播？(ii)滑移、开裂和失稳对整体塑性变形和损伤容限的协同效应是什么？(iii)非施密德效应对开裂和失稳的作用是什么？(iv)晶间裂纹是如何影响这些材料的多晶损伤容限的？该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

This Faculty Early Career Development (CAREER) grant will focus on quantifying the effects of microstructural deformation mechanisms on the mechanical response of materials with nanolayered crystal structures, such as zinc, mica, and certain carbides. These materials hold tremendous promise for technologies where reliable performance is required under extreme environments, such as at elevated temperatures. However, their use in critical applications is severely limited as they exhibit extremely direction-dependent (anisotropic) behavior, cannot accommodate an arbitrary shape change, and are essentially brittle. On the other hand, the anisotropy of these materials enables them to undergo macroscale deformation via crystal slip, cracking, and/or instability at smaller scales, which in turn can significantly enhance their damage tolerance and ductility. This research project will provide the fundamental understanding of the microstructure-based mechanical response of nanolayered crystalline materials, paving the possibility of microstructural engineering to harness their damage tolerance and ductility for applications. This objective will be achieved with an integrated experimental-computational approach, which will result in a predictive modeling framework and experimental data at several length scales. The research activities will be complemented with a series of fully integrated educational and outreach activities. The educational activities will enhance undergraduate and graduate level engineering education through development of interactive instructional materials and a new course. The outreach activities will increase awareness of engineering by engaging Texas high school teachers in research and students in a summer camp, respectively.The objective of this research is twofold. First, develop an understanding of the synergistic effects of crystallographic slip, cracking, and instability in extremely anisotropic nanolayered materials, oxides, carbides and nitrides, via novel small-scale in-situ experiments. Second, develop and validate a crystal plasticity-based constitutive model incorporating non-Schmid effects, cleavage-like cracking, and local instability to predict microstructure-sensitive mechanical response of these materials. This will provide answers to following key fundamental questions: (i) What material property or a combination of properties affect the onset and propagation of slip, cracking and instability in single crystals? (ii) What are the synergistic effects of slip, cracking and instability on overall plastic deformation and damage tolerance? (iii) What is the role of non-Schmid effects on the onset of cracking and instability? (iv) How does intergranular cracking affect the damage tolerance of polycrystals of these materials?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.