Control and design of response in disordered networks: Geometry and self-stresses.

The mechanical response of elastic networks is not only controlled by the elastic properties of its constituents, but also by their architecture. This is evident for crystalline structures, but equally true for random networks. I share two recent examples where we use geometry to elicit nonstandard mechanical response from disordered networks. In the first, we design freestanding frames that are mechanically overconstrained, and demonstrate that by engaging their states of self stress (i.e., applying internal loads that produce no strain) we can tune the overall mechanical response and induce softness, bi- and instabilities of purely geometric origin [1]. In the second example, we design random periodic lattices and structurally optimize them to exhibit specific responsiveness manifested, f.i., by extreme auxeticity (deeply negative Poisson's ratios). Together, these examples illustrate that the power of geometry may be harnessed to coax tailored, highly non-generic response even out of fully disordered materials.

[1] Phys. Rev. E 99, 023001 (2019)