Extreme Metamaterial Lattices

海绵状（细胞状）材料有许多用途，包括坐垫、清洁海绵、头盔和运动护垫等防护装备、漂浮和飞机的轻质板。传统上，毛孔的形状是不受控制的。增材制造（3D打印）最近可以更好地控制细胞材料的微观结构形状。超材料是具有不寻常或极端物理特性的材料。首先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，细胞微观结构所允许的自由度尚未得到充分利用。为了扩大设计的自由度，该奖项支持与海绵状固体材料非均质性相关的自由度的基础研究。从这项研究中获得的见解旨在产生更好的材料，避免在孔或裂缝周围集中应力。新材料将被开发出来，对温度和电场具有不同寻常的极端变形响应。我们期望这项研究能够与其他研究分支，包括材料科学、生物力学、地质力学以及纳米材料研究提供协同作用。与之前的项目一样，该奖项将允许本科生和少数民族学生参与研究，并将促进将研究成果纳入大学的教育使命。目前的细胞状固体，包括桁架晶格，已经用经典弹性来理解，现在知道这对这种材料来说是过度限制的。一种新型的极端晶格材料将被设计，通过增材制造合成和实验表征。这些非均相材料将比已知材料表现出更大的自由度。他们将受到广义连续统概念的启发。材料将具有可控的非定域性、应力集中免疫、泊松比控制、压电性和热膨胀以及多功能能力。3D材料将设计为高水平的压电和热弹性响应。将开发具有电场扭耦合、挤压扭耦合和温度扭耦合等新现象的材料。该研究旨在更好地理解存在应力集中的非均质材料，并提供新的工具，以合成不受应力集中影响的新材料，并期望其具有韧性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.