Experimental and numerical investigation of the energy absorption in hybrid double-hat thin-walled structures reinforced by adhesive bonding under three-point bending

In this paper, the energy absorption parameters of bolted double-hat joints reinforced by adhesive bonding were investigated. The objective of this article is to leverage adhesive bonding`s benefits to reinforce a double hat-shaped aluminum/steel energy absorber, thereby attaining the desired energy absorption characteristics before connection failure. This is achieved without inducing heterogeneous deformations in the structure and simultaneously reducing its overall weight, all while demonstrating superior outcomes compared to conventional methods and reaching the ability to predict adhesive failure in simulations. For this purpose, three different types of specimens were considered: aluminum (both substrates), steel (both substrates), and aluminum-steel (upper: aluminum, lower: steel). These specimens were joined via adhesive and bolt jointing techniques (bolt vs. bolt-adhesive hybrid joint). Experimental data showed that the behavior of the bolt-adhesive aluminum-steel hybrid structure shows the best energy absorption parameters. In order to represent the mechanical responses of the adhesively bonded structure in FEM, a bi-linear CZM was utilized to simulate the failure, indicating a good agreement between experimental and numerical results.