Stress control in non-ideal Maxwell lattices via geometry

Maxwell lattice, on the verge of mechanical instability, can demonstrate topologically polarized zero modes (ZMs) and state of self-stresses (SSSs) which lead to drastically different stiffnesses on opposite boundaries. It is known in idealized Maxwell lattice models that interfaces with localized SSSs can focus external stress and protect the bulk from fracturing. However, in non-ideal Maxwell lattices (i.e. additively manufactured) where thin ligaments with bending stiffness instead of free-hinges connect the rigid elements, stress accumulates at these ligaments in patterns not captured by the topological polarization. We computationally studied the effect of such bending stiffness in non-ideal Maxwell lattices in terms of stress distributions. We find that, by tuning the unit cell geometry, the stress distribution in these non-ideal Maxwell lattices can be controlled such that the amount of stress accumulated at the ligaments is small while the topological stress localization is preserved in the Maxwell lattice.