Heterogeneity and Anisotropy in Tough Materials

韧性是一种材料承受断裂的能力。对大多数结构材料来说，理解和预测这一关键特性仍然是一个重大挑战。在生物系统中，高韧性通常与复合微结构有关。通常，软的有弹性的蛋白质与硬的矿物晶体结合在一起，并有特定的取向。该项目将利用新的方法构建合成复合材料，其中材料成分可以以受控的方式排列，以实现大量不同的微结构。这些材料将进行机械测试，以确定它们的强度和韧性。为了预测裂纹的扩展，将生成材料的计算机模型，从而深入了解控制坚韧材料的关键物理原理。该项目将确定坚韧材料的关键特性。因此，预期的研究成果将提高构建具有最佳力学性能的材料的能力。本科生和高中暑期实习生将参与材料的施工和机械测试。将开发一个K-8模块，名为“坚韧”，向学生传授材料力学的基本原理，包括复合材料结构、部件的取向和材料属性。该项目将裂纹扩展的计算和实验研究相结合，以确定材料的各向异性和非均质性在裂纹路径选择和断裂韧性中的相对重要性。新型的合成不连续纤维复合材料将被制造出来，从而可以利用磁场来调节复合材料的不均匀和各向异性。数值模拟将使用相场方法来预测具有定义的各向异性和非均质性的材料中的复杂裂纹路径。裂纹扩展将在不同的加载方式下进行实验测量和计算预测。将研究裂纹与宏观非均质性的相互作用，以及各向异性材料中的裂纹扩展。通过这项研究，我们可以确定导致裂纹失稳的各向异性(弹性模数与断裂能)的类型和数量，这些不稳定性在二维和三维不同断裂模式下是如何表现的，以及各向异性和非均质性在促进裂纹偏转和增加韧性方面的相对重要性。

Toughness is a material's ability to withstand fracture. Understanding and predicting this key property remains a major challenge for most structural materials. In biological systems high toughness is commonly associated with composite microstructures. Often, soft flexible proteins are found in combination with a hard mineral crystal, organized with specific orientations. This project will utilize novel methods for constructing synthetic composite materials in which the material components can be arranged in a controlled way to achieve a large array of different microstructures. The materials will be tested mechanically to determine their strength and toughness. Computer models of the materials will be generated in order to predict crack propagation, giving insight into the critical physical principles governing tough materials. This project will determine critical characteristics of tough materials. Thereby, the anticipated research outcomes will improve the ability to construct materials with optimal mechanical properties. Undergraduate students and high school summer interns will be involved in the construction and mechanical testing of the materials. A K-8 module entitled 'Being tough' will be developed to teach students underlying principles of mechanics of materials, including composite structures, orientation of components, and material properties. This project combines computational and experimental studies of crack propagation to determine the relative importance of material anisotropy and heterogeneities in crack path selection and fracture toughness. Novel synthetic discontinuous fiber composites will be produced whereby inhomogeneity and anisotropy of the composite can be tuned with a magnetic field. Numerical simulations will employ the phase field method to predict complex crack paths in materials with defined anisotropy and heterogeneities. Crack propagation will be experimentally measured and computationally predicted in various loading configurations. The interaction of cracks with macroscopic heterogeneities, and crack growth in anisotropic materials will be investigated. With this research we can determine what type and amount of anisotropy (elastic moduli versus fracture energy) lead to crack destabilization, how these instabilities manifest for different modes of fracture in two and three dimensions, and what relative importance anisotropy and heterogeneity have in promoting crack deflection and increased toughness.