An understanding of shock wave propagation in materials is important for many aspects of Soldier protection, including ballistic and blast mitigation, as well for understanding failure analysis and fundamental material properties. Central to shock wave mitigation is the concept of impedance mismatch and disruption of wave propagation using dissimilar material interfaces. Molecular composites, such as those utilizing graphene or monolayer MoS2 as inclusions, represent a compelling opportunity to create extreme impedance mismatch in materials comprised exclusively of nanometer scale interfaces. This ISN-4 project seeks to explore a new class of molecular composite materials invented at MIT that can impose novel impedance mis-match architectures or self-reinforce via a variety of novel mechanisms in response to an incident shockwave, using the energy and deformation of the wave itself. The project will produce novel materials for fundamental investigations of wave propagation in highly anisotropic molecular composite stacks and scroll structures, tested using facilities at ARL. These materials are made possible using a series of new fabrication methods developed at MIT as a part of ISN-3, namely the 4j method and shear scrolling of 2D materials to produce planar and fiber composites.
The primarily goal of this project is the production of design principles for how discontinuous phonon waves can be directed, steered, concentrated and controlled using nanofabrication techniques. Ultrafast spectroscopic and imaging tools at both ARL and MIT will be leveraged to study shockwave propagation for comparison to modeling. Molecular simulation using reactive force fields will be used to understand shock propagation and material affects in molecular composites produced in this work. This project is designed to be highly integrated and synergistic with efforts at ARL that are actively exploring mechanisms of shock mitigation. This continues and extends a highly successful record of collaboration between the MIT and ARL laboratories, a key objective of the ISN. The overall outcome of this ISN effort will be to produce new insight into our understanding and control of shockwaves in composite materials. It will also produce new material architectures that have unique combinations of mechanical and other functionalities.