Optimizing properties on the critical rigidity manifold of underconstrained central-force networks

Our goal is to develop a design framework for multifunctional mechanical metamaterials that can tune their rigidity while optimizing other desired properties. Towards this goal, we first demonstrate that underconstrained central-force networks possess a critical rigidity manifold of codimension 1 in the space of their physical constraints. We describe how the geometry of this manifold generates a natural parametrization in terms of the states of self-stress, and then use this parametrization to numerically generate disordered network structures that are on the critical rigidity manifold and also optimize various objective functions, such as maximizing the bulk stiffness under dilation, or minimizing length variance to find networks that can be self-assembled from equal-length parts. This framework can be used to design mechanical metamaterials that can tune their rigidity and also exhibit other desired properties.