Dynamic response of multi scale periodic materials and structures

现代结构材料旨在以最小的重量获得高刚度、强度、韧性和阻尼性，以制造用于制造(移动机床结构)和运输(海军、航空航天和汽车工业的夹层板)的高效结构部件。将两种或更多材料组合在一起，可以创建一种新的混合材料，其性能优于其母材料，从而满足相互冲突的材料特性要求。在背景基质介质中使用颗粒或纤维的复合材料是材料水平上的杂化的例证。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，体现在使用粘结在两个面层材料之间的核心材料的夹层结构中。以上两个工程实践引出了一个问题：能否通过借用结构建筑中的例子，利用大小、比例和形状来设计混合材料？对这个问题的探索首先导致了金属和聚合物泡沫的发展，最近又导致了晶格材料的发展。这些新型周期性材料的开发不仅是为了满足高比刚度和高强度的结构效率要求，而且还为了满足其他功能要求，如良好的热响应和振动-声学响应。制造技术的最新发展，如快速成型、3-D打印、软光刻，为设计多功能结构材料的研究注入了活力。由于泡沫的随机微结构导致其刚性不足，现在人们的注意力转向了具有周期性微结构的材料。新兴的制造技术不仅提供了结合两种材料的能力，还提供了控制形状(微结构)和长度比例的能力，从而创造出创新的材料、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新的周期性复合材料的出现，这些材料具有良好的振声和动态响应特性。周期性在介观周期材料中被设计，而周期性是纳米材料所固有的，例如单层石墨烯(SLG)和碳纳米管(CNT)，其中碳原子排列在六方晶格中。在这两种尺度上，缺陷和非连续体的存在都是不可避免的。虽然原子间相互作用势是SLGS和CNTs中非线性的来源，但几何和材料的非线性与微桁架晶格材料有关。这项研究将研究微纳米尺度周期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。提出的研究涉及多尺度周期性材料和结构的动力响应。本研究的长期目标是通过理论和实验相结合的方法，了解微结构的尺度、形状和尺寸对周期性材料的有效力学性能、振动声学和波传播响应的影响。短期内，研究将集中在中尺度的周期性物质上。所产生的基础知识将被用于设计多功能结构和设备，用于制造、航空航天和生物医学行业。这种广泛的应用是可能的，因为采用了基本的积木方法。该研究项目将在未来五年内培训四名研究生(两名博士和两名MASC)，在这个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。

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.