Tailoring the characteristic length scale of 3D chiral mechanical metamaterials

The effects of chirality in elastic materials generally disappear in the large-sample limit, with an expected asymptotic scaling proportional to the inverse of the sample side length. Here, we show that the onset of this asymptotic scaling can be pushed towards very large characteristic lengths by proper tailoring of the unit cells of three-dimensional (3D) periodic mechanical metamaterials. By connecting chiral motifs via easily deformable intermediate elements, we suppress compensation effects that otherwise arise when directly connecting chiral motifs. In this manner, large chiral effects persist in 3D microlattices containing more than hundred thousand unit cells. Microstructures comprising that many unit cells will likely become accessible experimentally in the near future by next-generation 3D Additive Manufacturing. To cope with the numerics of such large yet finite systems, we consider architectures that can be approximated by using Timoshenko beam theory. (C) 2019 Elsevier Ltd. All rights reserved.