Investigating and Exploiting a New Strengthening Mechanism Found in Biomineralized Composites

许多活的生物体形成生物矿化复合物，组装在分层结构中用于保护目的或结构支撑（贝壳、骨、鹿角、牙本质等）。这些天然复合材料通常具有与其非生物矿化形式相比优异的机械性能。 这项工作利用了PI最近在鲍鱼壳中发现的一种新的强化机制。 特别是，在其自然栖息地的季节性变化中发现的贝壳中周期性生长中断的影响，类似于树木年轮。 初步结果表明，这些层的存在以及它们的厚度和周期性似乎赋予了壳体额外的强度。 这项工作的目的是确定的基本机制，通过这些增长中断赋予增强的行为的多层，复合壳。 特别是，它将在实验室中培养鲍鱼，并利用水温来触发它们的代谢系统，从而产生生长中断。 这些中断和珍珠层的材料性质将被表征为（1）在个体基础上，（2）作为双组分复合物和（3）作为多层复合物。 确定这些生物体如何利用结合层中不同材料特性的结构，将为工程师提供关于材料强度的新知识。它还将提供工具来设计具有增强属性和性能的新型复合体系结构。 这些无疑将影响从机械防护装甲到更强更轻的结构支撑，甚至到增强沥青道路的耐久性的应用。 该项目的跨学科性质在于物理学、生物学和工程学之间的接口，这是一个理想的环境，为学生提供教育和发展的技术和技术，有一个快速增长的需求。该项目旨在通过利用生物矿化复合材料中发现的结构和材料性能组合，实现多层复合材料强度和韧性的变革性进步。 它集中在珍珠层结构中生长中断的作用。 当生物体的代谢过程因其自然栖息地的季节性变化而中断时，就会发生这些中断，类似于树木的年轮。 这项工作将涉及在实验室环境中培养鲍鱼，使它们受到环境参数的影响，从而触发它们的代谢系统，产生生长中断。 将以这种方式调制壳架构以确定这些特性（厚度、周期性等）。赋予最大的强度和韧性。 这项工作的主要智力贡献包括：（1）提供了一个更好的理解和测量的个别材料性能（弹性模量，泊松比，硬度等）。（2）为基于泊松比失配的多层复合材料在机械防护应用中的优化响应提供了建筑和组合材料准则;以及（3）从而能够评估软体动物的自然选择是否充分发挥了这些多层膜的增韧机制，复合体系结构提供。

Many living organisms form biomineralized composites assembled in hierarchical architectures for protective purposes or structural support (sea shells, bone, antler, dentin, etc.). These natural composites often have excellent mechanical properties in contrast to their non-biomineralized forms. This work leverages a recent discovery by the PI of a new strengthening mechanism found in Abalone shells. In particular, the influence of periodic growth interruptions found in the shells from seasonal changes in its natural habitat, analogous to tree rings. Preliminary results show that the presence of these layers as well as their thickness and periodicity appear to impart added strength to the shell. This work is aimed at determining the fundamental mechanism by which these growth interruptions impart enhanced behavior to the multilayer, composite shell. In particular, it will culture the Abalone in the lab and use water temperature to trigger their metabolic system to generate growth interruptions. The material properties of these interruptions and the nacre will be characterized (1) on an individual basis, (2) as a two component composite and (3) as a multilayer composite. Ascertaining how these organisms utilize an architecture that combines different material properties in the layers would give engineers with new knowledge on material strength. It also will provide tools to design new classes of composite architectures possessing enhanced properties and performance. These undoubtedly would impact applications ranging from mechanically protective armor to stronger and lighter structural supports and even to enhanced durability of asphalt roads. The interdisciplinary nature of the project lies at the interface between physics, biology and engineering, which is an ideal setting for the education and development of students in technologies and techniques that have a rapidly growing demand.This project is aimed at enabling transformative advancements in the strength and toughness of multilayer composites by leveraging architectures and material property combinations found in biomineralized composites. It focusses on the role that growth interruptions play in the nacre structure. These interruptions occur when the organism's metabolic processes are interrupted from seasonal changes in its natural habitat, analogous to tree rings. This work will involve culturing Abalone in the laboratory setting, subjecting them to environmental parameters that trigger their metabolic system to generate a growth interruption. Shell architectures will be modulated in this way to determine those characteristics (thickness, periodicity, etc.) that impart maximum strength and toughness. The primary intellectual merit contributions of this work involve: (1) providing an improved understanding and measurement of the individual material properties ((elastic modulus, Poisson's ratio, hardness, etc.) of the nacreous and growth interruption materials as well as their interplay in determining composite behavior; (2) providing architectural and combinatory material guidelines for optimizing the response of multi-layered composites for mechanically protective applications based upon Poisson's ratio mismatch; and (3) enabling an assessment as to whether natural selection in mollusk organisms has fully maximized the toughening mechanisms that these multilayer composite architectures provide.