A review of advanced materials, structures and deformation modes for adaptive energy dissipation and structural crashworthiness

Thin-walled hollow structures capable of large plastic deformations are ubiquitously present in sacrificial, high-capacity energy absorbers. A significant challenge in the field of structural crashworthiness is the myriad of loading conditions that an entity can experience. For example, bumper frames are equally vulnerable to direct and oblique impacts, where the latter cases are particularly prone to instability, under a broad range of loading rates and geometric and mechanical properties of the target structure. Traditional energy absorbers are designed with a single, characteristic force–displacement response which must be carefully tuned to accommodate a comprehensive range of loading conditions. This review highlights and summarizes the extensive research efforts directed towards the development of more advanced, adaptive energy absorbers with tailored mechanical responses and specialized characteristics, including prescribed steady-state loading regimes, load-limiting behavior and multi-to​ omnidirectional load bearing capabilities. The novel concept of adaptive energy dissipation has recently emerged as a design philosophy intended to combat the diverse challenges in the field of structural crashworthiness by manipulating the structural and/or material properties of energy absorbers to enable more ideal, sophisticated mechanical responses. Passive adaptive energy absorbers are typically comprised of structures with varied (graded) dimensions, localized material refinement and/or compounded materials to yield structures which exhibit force responses with precisely designed corridors. The development efforts for active adaptive systems which can readily alter their geometry based upon data collected by external sensors to implement the preferred mechanical response for a given scenario, either before or during an impact event, are also showcased.