Tailoring of the Elastic Postbucking Response of Cylindrical Shells: A Route for Exploiting Instabilities in Mechanical Systems

Michigan State University, East Lansing MI

Investigators

Abstract

Elastic instability, which refers to the sudden loss of compression load carrying capacity of a structural element, is traditionally considered a failure limit. Yet, unstable behavior involves a sudden change of the structure's geometry and the release of accumulated energy. Thus, a new way of thinking is emerging for using the unstable response of slender structures for purposes that seem to be rapidly increasing and diversifying. Cylindrical shells are among the structural elements most affected by instabilities (commonly seen as a negative trait) but their geometry provides unique opportunities for controlling their unstable response, which can display multiple unstable transitions in a recoverable manner. The research hypothesis is that cylindrical shells can be designed such that their unstable response is controlled through optimal geometric and material stiffness distributions on the shell surface. The research findings will create new possibilities for the development of materials and devices that use instabilities for applications such as sensing, actuation, control, energy harvesting, and energy dissipation; advances that in turn could also facilitate the development of novel smart, active and multifunctional materials and structures. The project will allow training of a Ph.D. student and educational and outreach components will broaden access to the project's core knowledge to undergraduate and high-school students. The core research idea is that the features in the far elastic postbuckling response of cylindrical shells can be fully characterized, modified, and potentially tailored. The features of interest are not the initial elastic stiffness or the first bifurcation load, but a response with multiple stable to unstable transitions, the equilibrium path loading stiffnesses, the released kinetic energy at critical point transitions, and the dissipated energy during cyclic loading. Topology and shape optimization techniques will be expanded to achieve the desired response and experiments will validate computational designs and finite-element based simulations. Analysis and design frameworks will be developed for axially loaded cylinders with controllable elastic postbuckling behavior. The key innovation will be proving that the elastic postbuckling response of cylindrical shells can be tailored through the design of material and geometric features on the shell's surface, thus transforming a behavior traditionally seen as undesirable into an opportunity for use in smart materials and structures. The research will generate new knowledge on the extent and means to control and design the elastic postbuckling response of cylindrical shells, which will provide new concepts and guidance for the use of tailorable structural instabilities.