Abstract: An energy absorbing cell has a first structural element, a second structural element disposed parallel to and spaced apart from a first structural element, a first intermediate member, and a second intermediate member. Each intermediate member is disposed at an angle between the structural elements. A first end and a second end of each intermediate member are respectively attached to the structural elements. The intermediate members are formed from an elastic material. The angles of the intermediate members are selected such that application of a compressive force to displace the structural elements toward one another triggers a snap-through instability in both intermediate members. The energy absorbing cell is used, singly or in combination with one or more other energy absorbing cells, to form energy absorbing structures, such as vehicle bumpers or highway barriers, adapted to control the deceleration of an object impacting the energy absorbing structure.

Abstract: Void structures, systems and devices with void structures, and methods of fabricating void structures are disclosed. A void structure is disclosed with a repeating elongated-aperture pattern designed to provide negative Poisson's Ratio behavior under macroscopic stress and strain loading. The pattern can include horizontal and vertical elliptically shaped apertures that are arranged on horizontal and vertical lines in a way that the lines are equally spaced in both dimensions. The centers of each aperture is on a crossing point of two of the lines. The vertical and horizontal elliptically shaped apertures alternate on the vertical and horizontal lines such that any vertical aperture is surrounded by horizontal apertures along the lines (and vice versa), and the next vertical apertures are found on both diagonals. The voids can also act as cooling and/or damping holes and, due to their arrangement, also as stress reduction features.

Abstract: A low porosity sheet material comprising an arrangement of elongated void structures, each of the elongated void structures including one or more substructures, a first plurality of first elongated void structures and a second plurality of second elongated void structures, each of the first and second elongated void structures having a major axis and a minor axis, the major axes of the first elongated void structures being perpendicular to the major axes of the second elongated void structures, the first and second pluralities of elongated void structures being arranged in an array of rows and columns, each of the rows and each of the columns alternating between the first and the second elongated void structures, wherein a porosity of the elongated void structures is below about 10%.

Abstract: A transformative periodic structure includes a plurality of elastomeric or elasto-plastic periodic solids that experiences a transformation in the structural configuration upon application of a critical macroscopic stress or strain. The transformation alters the geometric pattern changing the spacing and the shape of the features within the transformative periodic structure. For the case of elastomeric periodic structures upon removal of the critical macroscopic stress or strain, the transformative periodic solids are recovered to their original form. For the case of elasto-plastic periodic structures upon removal of the critical macroscopic stress or strain, the new pattern is retained. Polymeric periodic solids can be recovered to their original form by heating or plasticizing.

Abstract: A transformative periodic structure includes a plurality of elastomeric or elasto-plastic periodic solids that experiences a transformation in the structural configuration upon application of a critical macroscopic stress or strain. The transformation alters the geometric pattern changing the spacing and the shape of the features within the transformative periodic structure. For the case of elastomeric periodic structures upon removal of the critical macroscopic stress or strain, the transformative periodic solids are recovered to their original form. For the case of elasto-plastic periodic structures upon removal of the critical macroscopic stress or strain, the new pattern is retained. Polymeric periodic solids can be recovered to their original form by heating or plasticizing.