This Faculty Early Career Development Program (CAREER) project will focus on an integrated research and educational effort to derive fundamental knowledge about the role of defects on wave motion in dry or immersed granular materials. The program will also investigate the capability of ordered granular crystals to adapt their structure via defect generation using external fields for better protection against impact. The current strategy for design of granular crystals and other metamaterials focuses on optimizing fixed structures for specific applications such as shock absorption and impact protection. This program presents a significant change in design philosophy to sense-adapt-recover approach where granular crystals would adapt their internal structure using external fields based on basic sensor data (velocity, direction of incoming projectile) to achieve a specified objective (such as protection from incoming projectile) and revert to their original state. This will help transform the design of hazard protection gear (such as vests, helmets) for military, sport and construction sectors, impact/shock protection systems for underground / underwater infrastructure and excellent lightweight alternative for structural damping in various civilian and defense applications. The program will also identify (1) junior-level projects to study socio-technical applications of the research efforts, and (2) senior-level capstone design projects to perform complementary research activities. The program would promote diversity in STEM disciplines by active recruitment of under-represented minorities and women candidates in research as well as K-12 outreach activities involving the classroom teaching modules and hands-on experience with simplified experiments.
The research project would explore two novel strategies for adaptive dissipation and impact mitigation via defect generation using external fields: (1) dry granular crystals consisting of active polymer grains and (2) granular crystals immersed in active rheological fluids (magnetorheological fluids, shear-thickening fluids). The wave scattering and attenuation effects around a point defect in a 1D granular chains or 2D granular crystals are well established. Thus, the unique ability to introduce defect patterns will allow for highly effective control of the magnitude and direction of the stress wave propagation in granular crystals. The research efforts will establish a comprehensive understanding of two fundamental issues; how wave motion in dry or immersed granular crystals is affected by point or line defects and how the interactions between multiple defects influences the wave motion. The semi-empirical models describing the interaction between multiple defects in granular crystals will make a significant contribution to the continuum modeling of random particulate media utilized in various fields such as medicine, construction, defense and geology. Since dry, cohesion-less contact is difficult to realize at the micro/nanoscale, the research efforts on immersed granular crystals and their actuation using active rheological fluids would have significant implications on the miniaturization of granular metamaterials.
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.
