Graded Elastic Metamaterials: Rainbow Reflection, Topological Trapping, and Zero Group Velocity Modes

Graded elastic metamaterials have been identified as attractive candidates for the manipulation of waves on elastic beams and half-spaces with a variety of applications ranging from vibration isolation to energy harvesting. This talk will cover a review of the elastic metawedge (proposed by Colombi et al [Sci Rep, 6, 27717 (2016)]), highlighting several modalities through interpretation of local dispersion curves which underpin the phenomena of rainbow reflection, trapping, and mode conversion. Applications of each of these effects shall be outlined: rainbow trapping and rainbow reflection are delineated, providing a route to enhanced energy harvesting by inspection of zero group velocity modes; topological interfaces are incorporated within a grading structure, motivating robust energy harvesters; and finally designer diffraction for 'focussing' is achieved through mode conversion along a graded structure and at abrupt interfaces.