Frictional Mechanical Metamaterial

Common cellular and porous materials deform and absorb energy mainly through bending, stretching, and compression of continuously connected phases. In contrast this new category of mechanical metamaterials, named frictional mechanical metamaterials (FMM), are composed of separated but interacting components that dissipate energy through internal friction between components as they engage with each other. The new concepts, methodology, and tool sets developed in this research will not only create new knowledge in fundamental mechanics, but also will bring broad technical revolutions to leverage the fast advancements of mechanical metamaterials, additive manufacturing, and material science. The potential applications for new FMMs include protective materials, energy materials, soft robotics, actuators, dampers, adhesives, seismic engineering, and biomedical engineering. Customized STEM education activities under the theme of ‘Magic Friction’ will be designed and launched with support from the Center of STEM Education at Northeastern University. The education and outreach activities will focus on attracting and retaining students from underrepresented groups by promoting new design concepts for achieving unusual material properties and behaviors based off traditional mechanical engineering topics. This project will make fundamental contributions to the mechanics of materials and structures in theoretical, experimental, and numerical aspects by bridging the frontiers of the fields of mechanics, materials, mechanical metamaterials, and advanced additive manufacturing at both macro- and micro/nano- scales. For conventional materials, resilience and hysteresis often conflict with each other. The FMMs provide a platform to achieve both properties simultaneously. To amplify energy dissipation efficiency, auxeticity is utilized to promote internal friction in multiple directions, and chirality is employed to generate coupled sliding and rotational friction. Under the general goal, three specific objectives are planned: Objective I: To advance fundamental mechanics of friction under complicated conditions; Objective II: To explore mechanical behaviors of various engaging key-channel pairs; Objective III: To generate internal friction in multiple directions via auxeticity. Prototypes will be fabricated via 3D printing in both macro and micro scales. Innovative designs will be generated. An integrated analytical, numerical, and experimental methodology will be used for systematic investigation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.