Disordered nonlinear metamaterials for impact mitigation

Metamaterials designed for passive wave transformation have led to advancements in multiple fields, including acoustics, vibration isolation, and impact mitigation. Nonlinearity enhances signal tunability, yet current progress has been mainly limited to quasi-static studies. Previous findings [1] indicate that fine-tuning the nonlinear response alone can reduce the peak transmitted kinetic energy in the material by two orders of magnitude in a periodic and homogeneous system.

This study investigates how the introduction of spatial disorder affects dynamic wave attenuation in nonlinear metamaterials and provides guidelines for designing such systems for impact mitigation. The material system is idealized as a one-dimensional mass-spring-damper chain, where the nonlinearity at each unit cell is expressed as distinct polynomial force- displacement relations, and its impact dynamics are explored via discrete element modeling simulations. By employing a gradient-based optimization method, we discover configurations that would maximize a chosen dynamic performance metric, such as kinetic energy absorption or minimizing the peak transmitted force in the material. Our results indicate that a disordered nonlinear system can achieve up to four times better performance compared to a homogenous counterpart. We highlight the strong sensitivity to nonlinearity and demonstrate the physical realization of such mesostructured material systems.

References

[1] B. MacNider, H. Xiu, C. Tamur, K. Qian, I. Frankel, M. Brandy, H. A. Kim, and N. Boechler , Customizable wave tailoring nonlinear materials enabled by bilevel inverse design, (under review) https://arxiv.org/abs/2403.15725 (2024)