Bio-inspired selective nodal decoupling for ultra-compliant interwoven lattices

Abstract

Architected materials such as lattices are capable of demonstrating extraordinary mechanical performance. Lattices are often used for their stretch-dominated behavior, which gives them a high degree of stiffness at low-volume fractions. At the other end of the stiffness spectrum, bending-dominated lattices tend to be more compliant and are of interest for their energy absorption performance. Here, we report a class of ultra-compliant interwoven lattices that demonstrate up to an order of magnitude improvement in compliance over their traditional counterparts at similar volume fractions. This is achieved by selectively decoupling nodes and interweaving struts in bending-dominated lattices, inspired by observations of this structural principle in the lattice-like arrangement of the Venus flower basket sea sponge. By decoupling nodes in this manner, we demonstrate a simple and near-universal design strategy for modulating stiffness in lattice structures and achieve among the most compliant lattices reported in the literature.

Improved mechanical performance of quasi-cubic lattice metamaterials with asymmetric joints

“…with increased bending-dominated behavior) with s = 3/2 and s = 2. In the last limiting case (s = 2) the structure can become fully disintegrated inside the unit cells similarly to the recently proposed interwoven lattices with decoupled nodes 42 , but with straight struts. In such case the long struts will be connected only to the outer solid face plates of the sandwich-type specimens used in the experimental tests.…”

“…6) for the standard cubic structures can be significantly increased then by using proposed quasi-cubic lattices. In contrast to the known asymmetrization 41 and nodes decoupling methods 42 , in the present case we provide the preserving or even some increase of the static stiffness and strength in comparison with the ideal structures. The effect is reached by using small relative offsets (less then the struts diameter) in the unit cells with almost the same density and the same diameters of the straight struts as those in the ideal standard lattices.…”

“…The design for the interwoven lattices with improved energy absorption capacity have been also suggested recently in Ref. 42 , where the highly compliant structures were generated using the selectively decoupling nodes in bending-dominated lattices. In contrast to this work, we do not generate the zig-zag type struts remaining them straight.…”

Unravelling the mechanics of knitted fabrics through hierarchical geometric representation

“…yarn-and fabric-level) at the structural level not only causes a range of interesting physical phenomena [1,2] to arise but also provides a huge design space for functionalities in knitted fabrics beyond what their constitutive materials can achieve [3], echoing a wide range of research interests to design functional materials [4][5][6][7]. Knitted fabrics, analogous to some architected and bio-inspired materials [8][9][10][11], represent non-biological examples of a nonlinear elastic response characterized by a 'J-shape' curve, as the fabric transitions from bending energy dominant region to stretching energy dominant region under uniaxial tension. The presence of mesoscale stitch patterns enables the fabric to take on substantial tensile stress elastically.…”