Extreme Metamaterial Lattices

海绵(蜂窝)材料用于许多用途，包括座垫、清洁用海绵、头盔和运动垫等防护装备、漂浮以及飞机的轻质面板。传统上，毛孔的形状并不受控制。最近，添加制造(3D打印)允许更好地控制多孔材料中微结构的形状。超材料是指具有不寻常或极端物理性质的材料。其中第一个是我们实验室开发的负泊松比材料。与橡胶和普通材料相比，这些材料在拉伸时会膨胀。然而，细胞微结构所允许的自由并没有得到实质性的利用。为了扩大设计的自由，该奖项支持与海绵状固体中的材料异质性相关的自由的基础研究。从这项研究中获得的见解旨在制造出避免应力集中在孔洞或裂缝周围的优质材料。将开发对温度和电场具有异常和极端变形响应的新材料。我们期望这项研究能与材料科学、生物力学、地质力学以及纳米材料研究等其他学科产生协同效应。与以前的项目一样，该奖项将允许本科生和少数族裔学生参与研究，并将促进将研究成果纳入大学的教育使命。目前的蜂窝状固体，包括桁架格子，已经被用经典弹性来理解，这现在被认为对这类材料过于严格。一类新型的极端晶格材料将被设计，通过加法制造合成并进行实验表征。这些非均质材料将比已知材料表现出更多的自由。他们将受到广义连续统概念的启发。材料将具有可控的非局部性、抗应力集中、控制泊松比、压电性和热膨胀以及多功能能力。3D材料将被设计为具有高水平的压电和热弹性响应。出现电场-扭转耦合、挤压-扭转耦合和温度-扭转耦合等新现象的材料将得到发展。这项研究旨在更好地了解存在应力集中的异质材料，并提供新的工具，使合成不受应力集中影响的新材料成为可能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Spongy (cellular) materials are used for many purposes including seat cushions, sponges for cleaning, protective gear such as helmets and athletic pads, for flotation, and in lightweight panels in aircraft. The shape of the pores has not traditionally been subject to control. Additive manufacturing (3D printing) has recently allowed greater control over the shape of the microstructure in cellular materials. Metamaterials are materials with unusual or extreme physical properties. Among the first are the negative Poisson's ratio materials developed in our laboratory. These materials expand when stretched in contrast to rubber and common materials. Nevertheless, the freedom allowed by cellular microstructure has not been substantially exploited. To expand the freedom of design, this award supports fundamental research on the freedom associated with material heterogeneity in spongy solids. Insights from this study are intended to lead to superior materials that avoid concentration of stress around holes or cracks. New materials are to be developed with unusual and extreme deformation response to temperature and electric fields. We expect that the research to provide synergism with other branches of study including materials science, biomechanics, geomechanics and as well as nano-materials research. As with prior projects, this award will allow undergraduate students and minority students to participate in research and will facilitate incorporation of the fruits of research in the educational mission of the university. Current cellular solids, including truss lattices, have been understood using classical elasticity which is now known to be overly restrictive for such materials. A novel class of extreme lattice materials will be designed, synthesized via additive manufacturing and experimentally characterized. These heterogeneous materials will exhibit more freedom than known materials. They will be inspired by generalized continuum concepts. Materials will feature controlled nonlocality, immunity from stress concentration, control of Poisson's ratio, piezoelectricity and thermal expansion and multifunctional capacity. 3D materials will be designed for high levels of piezoelectric and thermoelastic response. Materials exhibiting new phenomena including electric field-twist coupling, squeeze-twist coupling and temperature-twist coupling will be developed. The research is intended to achieve better understanding of heterogeneous materials in the presence of stress concentrations and to provide new tools to enable the synthesis of new materials that are immune to stress concentration ands are expected to be tough.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.