Microstructural Effects in Tayloring the Response of Engineered Bio-Materials

这项研究的目标是建立基本的微观结构，性能的理解需要开发的新一代生物工程材料的特点是波浪形的微观结构，其目标性能是通过微观结构的基础上生存的进化实现的适者生存的原则。韧性，可扩展性和适应性可以实现通过开发各种安排的波浪形微观结构，但这些建筑特征相对于材料的反应缺乏基本的理解。PI及其同事最近的微观结构模拟研究表明，层厚度对非弹性域中具有波状微观结构的周期性多层的均匀化响应具有重大影响。拟议的调查解决了最近发现的这种效应和相关效应，首次在工程材料中模拟有限变形域（包括某些组织）中的生物材料反应。特别是，研究将回答以下问题，尚未解决的，在分析和开发的工程材料与刚性特性的生物医学应用：（1）什么是层厚度的均匀化和局部响应的波动周期性多层在有限变形域的影响？(2)具有波浪形微结构的工程材料的目标响应是否可以使用一种以上的微结构来实现？(3)复杂和简单之间的联系可以通过进化设计建立起来吗？该研究采用了一种基于PI，他的学生和合作者开发的称为参数有限体积直接平均微观力学（FVDAM）理论的新型均匀化技术的计算方法。该理论特别适合于非均质材料的稳健分析、模拟和优化，其精度可与有限元法相媲美，有限元法目前是计算标准，但效率更高。实验测量三种类型的二尖瓣腱索的反应，其表现出由排列在波浪层中的原纤维束的不同卷曲模式引起的不同水平的硬化，的验证和微观结构优化的调查组成部分的支持。智力的优点源于两个知识，将产生和从必要的理论工具，以实现它的进一步发展。很少有工作的基础上的第一原则已被报道，这是旨在解决生物组织中的微观结构对整体响应的影响。这项研究将为在生物医学应用中发挥重要作用的特定材料系统建立这种联系。此外，所提出的参数FVDAM理论的理论增强将在理论的演变中产生范式转变，有可能在非均质材料的分析和设计中取代现行的计算标准。由此产生的计算技术将很容易在跨多个学科边界的应用中使用，包括传统和新兴的具有生物灵感架构的工程材料。理论上的增强涉及到有限变形能力纳入FVDAM框架和随之而来的发展稳定和准确的算法的解决方案的结构力学问题的有限变形域，这仍然是一个焦点的数值工程界。所提出的研究是一个重要的一步，参数FVDAM理论？的持续发展需要实现其跨学科边界的全部潜力。更广泛的影响源于广泛的应用，其中具有波浪多层图案的材料和结构部件在多个尺度和学科中被利用，从波纹结构板到快速发展的纳米技术领域。具有波状结构的微结构可以潜在地增强某些性能特征，例如刚度、热稳定性和韧性。然而，在无穷小和有限变形领域解决这些问题的系统数据却很少。此外，开发的计算技术将以图形用户界面的形式提供给相关社区，以促进材料系统的分析、设计和开发，使材料科学家和结构力学家能够研究假设情况，以追求优化和耐用的材料微观结构。同时，它将通过培训本科生和研究生来实现更大的教育目的。通过PI从传统上代表性不足的群体中招募本科生？作为本科课程的讲师，以及通过著名的弗吉尼亚大学多样性中心，将参与GUI？作为暑期实习生，他们将在毕业论文中进一步利用这一经验。

The goal of this research is to establish fundamental microstructure-property understanding needed for the development of a new generation of bio-engineered materials characterized by wavy microstructures, whose targeted performance is attained through micro-structural evolution based on the survival-of-the-fittest principles. Toughness, extensibility and adaptability may be realized through the exploitation of various arrangements of wavy microstructures, yet fundamental understanding of these architectural features vis-a-vis material response is lacking. Recent micro-structural simulation studies by the PI and co-workers demonstrated that layer thickness has a substantial impact on the homogenized response of periodic multi-layers with wavy microstructures in the inelastic domain. The proposed investigation addresses this recently discovered effect, and related effects, for the first time in engineered materials that mimic biological material response in the finite-deformation domain, including certain tissues. In particular, the investigation will answer the following questions, which have not been yet addressed, in the analysis and development of engineered materials with stiffening characteristics for bio-medical applications: (1) what is the effect of layer thickness on the homogenized and local responses of a wavy periodic multilayer in the finite-deformation domain?; (2) can targeted response of an engineered material with wavy microstructure be achieved using more than one microstructure?; (3) can connection between complexity and simplicity be established through an evolutionary design?The investigation employs a computational approach based on a novel homogenization technique called the parametric finite-volume direct averaging micromechanics (FVDAM) theory developed by the PI, his students and collaborators. This theory is particularly well suited for robust analysis, simulation and optimization of heterogeneous materials with accuracy comparable to the finite-element method, which presently is the computational standard, but with substantially greater efficiency. Experimentally measured response of three types of mitral valve chordea tendinea, which exhibit different levels of stiffening caused by different crimp patterns of the fibril bundles arranged in wavy layers, is employed in support of the verification and microstructural optimization component of the investigation.The intellectual merit stems both from the knowledge that will be generated and from further development of the theoretical tools necessary to accomplish it. Very little work based on first principles has been reported which is aimed at addressing the effect of microstructure in biological tissues on the overall response. The investigation will establish this connection for a particular material system that plays a significant role in biomedical applications. Further, the proposed theoretical enhancements of the parametric FVDAM theory will produce a paradigm shift in the theory's evolution, with the potential to replace the prevailing computational standard in the analysis and design of heterogeneous materials. The resulting computational technology will be readily employed in applications across several interdisciplinary boundaries, including traditional and emerging engineered materials with bio-inspired architectures. The theoretical enhancements involve the incorporation of finite-deformation capability into the FVDAM framework and the concomitant development of stable and accurate algorithms for the solution of structural mechanics problems in the finite-deformation domain, which continue to be a focus of the numerical engineering community. The proposed research is an important step in the parametric FVDAM theory?s continued development needed to realize its full potential across disciplinary boundaries. The broader impacts stem from the wide range of applications in which materials and structural components with wavy multilayer patterns are utilized across several scales and disciplines, ranging from corrugated structural panels to the rapidly developing nanotechnology areas. Microstructures with wavy architectures can potentially enhance certain performance characteristics such as stiffness, thermal stability and toughness. Yet, little systematic data is available addressing these issues in both the infinitesimal and finite-deformation domains. Moreover, the developed computational technology will be made available to the pertinent communities in the form of a Graphical User Interface to facilitate analysis, design and development of material systems for a wide range of applications, enabling material scientists and structural mechanicians alike to investigate what-if scenarios in pursuit of optimized and durable material microstructures. Concurrently, it will serve a greater educational purpose through training of both undergraduate and graduate students. Undergraduate students recruited from traditionally under-represented groups through the PI?s contact as an instructor in undergraduate courses, as well as through the well-known Center for Diversity at the University of Virginia, will be involved in the GUI?s testing and applications as summer interns who will further exploit this experience in their senior theses.