Periodic topological lattice with different indentation hardness on opposite surfaces

Abstract

Different surface properties are needed simultaneously in many applications, especially under an indentation load or impact load. This study proposes one class of novel periodic topological mechanical metamaterials, 2D topological honeycomb structure and 3D topological lattice, whose opposite surfaces have significantly different indentation hardness. The difference of hardness is predicted by theoretical analysis and validated by simulations and experiments, which can be up to 7 times. In comparison with the traditional honeycomb structure with the same parameters, the topological honeycomb structure exhibits higher resistance to indentation loads and it can reduce the influence range and degree of indentation loads at the same time. A design guide of parameters is proposed to achieve a more significant difference of hardness between the opposite surfaces. General design rules at the level of both basic unit piece and lattice structure are proposed, which renders the topological lattice to have outstanding designability to meet different demands in applications. The topological lattice concept will open new avenues to design asymmetric structures and expand the existing design space of mechanical metamaterials. Keywords: Topological lattice, Mechanical metamaterials, Hardness, Indentation, Asymmetric structures