Design of heat-reversible snap joints for space frame bodies

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Design of heat-reversible snap joints for space frame bodies

Shalaby, Mohammed / Saitou, Kazuhiro

Aluminum space frame is considered as the next generation car body structure. One of the challenges in improving the recyclability of the aluminum space frame body structure is the clean separation of incompatible materials used in various body components, in particular, extruded aluminum structural frames and stamped (or sometimes injection-molded) external panels. In the current aluminum space frame bodies, joining between the internal frames and the external panels is achieved using permanent joints such as self-piercing rivets and resistance spot-welding. These permanent joints can only be detached destructively, inevitably leaving residues of mating materials that prevent the 'closed loop' recycling of aluminum alloys. This paper presents the design of new joints, heat-reversible snaps, which allow easy, non-destructive, and clean detaching between internal frames and external panels in automotive bodies. It is expected to dramatically reduce the end-of-life environmental impacts of the aluminum space frame bodies, which currently suffer from poor material recyclability. While the assembly process is analogous to normal locator-snap systems, the heat-reversible snaps can be unlocked nondestructively upon heating the panel at a certain location, via the non-uniform thermal deformation of the panel. The optimum number and locations of the locators on the given panel are found based on the equivalent springs that represent the stiffness of the locator. Then, the locations of snaps and heating that ensure unlocking upon heating of the minimum area on the panel are obtained. Finally, a case study on an automotive fender panel assembly is discussed.