The mechanical performance of adhesive joints containing active disbonding agents

Abstract A controllable adhesive disbonding mechanism can be achieved by incorporating, and then activating, functional additives located within the matrix of an adhesively bonded joint. This action facilitates the disassembly and material recovery of structurally bonded assemblies. The engineering capabilities of bonded joints containing a range of chemical or physical foaming agents were investigated. Joint disassembly was measured as a function of additive chemistries, physical properties and concentration. The short- and long-term mechanical properties of bonded joints and bulk adhesives containing functional additives were subsequently evaluated. The disbonding mechanism was found to be due to a ‘solid-state foaming’ of the adhesive, followed by a proliferation of micro-cracking throughout the matrix. The effect of the physical foaming agents on joint disassembly was mostly attributable to the volumetric expansion efficiency of the additive whilst constrained within an adhesive matrix. For chemical foaming agents, the effectiveness of disassembly was dependent on the chemical compatibility of the adhesive and additive, the concentration and the efficiency to which the additive decomposed to a gas.