Dynamic response of multi scale periodic materials and structures

现代结构材料旨在以最小的重量实现高刚度，强度，韧性和阻尼，以构建用于制造（移动机床结构）和运输（海军，航空航天和汽车工业的夹心板）的高效结构部件。结合两种或两种以上的材料，通过创造一种性能优于其母材料的新混合材料，满足了相互冲突的材料性能要求。在背景基质介质中使用颗粒或纤维的复合材料说明了材料水平上的杂交。这些轻质材料的工程应用可以进一步加强，在结构层面上，通过扩展相同的杂交思想，体现在夹层结构中，在两个面板材料之间使用粘合的核心材料。以上两个工程实践引出了这样一个问题：是否可以通过借鉴结构建筑的例子，利用尺寸、规模和形状来设计混合材料？为了回答这个问题，首先导致了金属和聚合物泡沫以及最近的晶格材料的发展。这些新型周期性材料正在开发中，不仅要满足高比刚度和强度的结构效率要求，还要满足其他功能要求，如良好的热和振声响应。快速成型、3d打印、软光刻等制造技术的最新发展，激发了设计多功能结构材料的研究。考虑到泡沫材料由于其随机的微观结构而缺乏刚度，现在人们的注意力转向了具有周期性微观结构的材料。新兴的制造技术不仅提供了结合两种材料的能力，而且还控制了形状（微结构）和长度尺度，从而创造了创新的材料、结构和设备。通过设计周期性微结构来控制波和声响应的能力导致了一类具有良好振动声学和动态响应特性的新型周期性复合材料的出现。虽然周期性是在中尺度周期材料中设计的，但周期性是纳米材料（如单层石墨烯（SLG）和碳纳米管（CNT））所固有的，其中碳原子排列在六边形晶格中。在这两个尺度上，缺陷和非线性源的存在是不可避免的。原子间电位是slg和CNTs中非线性的来源，而几何非线性和材料非线性则与微桁架晶格材料有关。提出的研究将研究微纳米尺度周期性材料的线性和非线性动态响应，特别是在存在缺陷和耗散机制的情况下。提出的研究是关于多尺度周期材料和结构的动力响应。本研究的长期目标是将理论与实验相结合，了解微观结构尺度、形状和尺寸对周期性材料的有效力学性能、振声和波传播响应的影响。短期内将集中研究中尺度的周期性物质。所产生的基础知识将被用于设计多功能结构和设备，应用于制造业、航空航天和生物医学行业。由于所采用的基本构建模块方法，这种广泛的应用是可能的。该研究计划将在未来五年内在全球研究界和加拿大航空航天和制造业感兴趣的新兴领域培养四名研究生（2名博士和2名硕士）。

Modern structural materials are designed to achieve high stiffness, strength, toughness and damping with minimum weight to build efficient structural components used in manufacturing (moving machine tool structures) and transportation (sandwich panels in naval, aerospace and automotive industries). Combining two or more materials fulfils the conflicting material property requirements by creating a new hybrid material with properties superior to those of its parent materials. Composite materials using particles or fibres in a background matrix medium are illustrative of hybridization at the material level. Engineering application of these lightweight materials can be further enhanced, at the structural level, by extending the same idea of hybridization, embodied in sandwich construction using a core material bonded between two face sheet materials. The above two engineering practices lead to the question: can one design hybrid materials by borrowing examples from structural construction utilizing size, scale, and shape? The quest to answer this question has first lead to the development of metal and polymeric foams and more recently lattice materials. These new class of periodic materials are being developed to fulfil not only the structural efficiency requirements of high specific stiffness and strength, but also other functional requirements such as favourable thermal and vibro-acoustic response. Recent developments in manufacturing technologies such as rapid prototyping, 3-D printing, soft lithography have invigorated research to design multifunctional structural materials. Given the lack of stiffness of foams due to their random micro-architecture, attention has now turned onto materials with periodic microstructure. Emerging manufacturing techniques not only offer the ability to combine two materials but also control the shape (micro-architecture) and length scale leading to the creation of innovative materials, structures, and devices. The ability to control wave and acoustic response by designing periodic microarchitecture has led to the emergence a new class of periodic composite materials with promising vibroacoustic and dynamic response characteristics. Whereas periodicity is engineered in mesoscale periodic materials, periodicity is intrinsic to nanomaterials such as Single Layer Graphene (SLG) and Carbon Nanotubes (CNT), wherein carbon atoms are arranged in a hexagonal lattice. At both scales the presence of defects and sources of nonlienarity are unavoidable. While interatomic potentials are the sources of nonlinearity in SLGs and CNTs, geometric and material nonlinearities are relevant to micro truss lattice materials. The proposed research will study linear and nonlinear dynamic response of micro and nanoscale periodic materials particularly in the presence of defects and dissipation mechanisms. The proposed research is concerned with dynamic response of multiscale periodic materials and structures. The long-term goal of this research, combining theory and experiments, is to understand the influence of microstructural scale, shape, and size on effective mechanical properties, vibro-acoustic, and wave propagation response of periodic materials. The research will focus on periodic materials at mesoscale in the short-term. Fundamental knowledge generated will be exploited to design multifunctional structures and devices for applications in manufacturing, aerospace, and biomedical industries. Such wide-ranging applications are possible due to the basic building-blocks approach pursued. This research program will train four graduate students (2 PhDs and 2 MAScs) over the next five years in this emerging area of interest to global research community and Canadian aerospace and manufacturing industries.