Tailorable Adhesives for Multi-material Joining, Facile Repair and Re-assembly

Abstract

Joining of materials and components is inevitable as it allows versatility in assembly and repair along with reduction in time and cost of manufacturing. This work uses ‘active adhesives’ that inherit all the benefits of bonded joints, such as lightweight, eliminate holes and associated stress-concentrations, and overcomes the shortcomings of disassembly and repair. Thermoplastic adhesives modified by the incorporation of electrically conductive graphene nanoplatelets at a concentration above the percolation point provide a unique synergy of mechanical, thermal and electrical properties. While the choice of the thermoplastic is governed by the desired application the addition of the graphene nanoplatelets allows energy to be deposited primarily in the adhesive. The percolated network of graphene particles in the adhesive at less than 2% can quickly couple to high frequency radiation (microwave, or MW) via non-contact methods and increase the adhesive temperature to above the required processing temperatures. The adhesive melts and flows over the adherends and upon cooling forms a structural adhesive bond. Furthermore, the process can be used to disassemble the adhesive joint if repair or reworking is required. In this work, the concept of aforementioned active adhesives was studied using varying graphene contents in nylon-6 adhesive. Activation and re-assembly was studied on in-plane (lap-shear) joints. Structural behavior of re-assembled joints was found to be similar to thermally bonded joints. Overall, active adhesives such as the ones attempted in this work have a great potential in a wide range of applications wherein in-situ repair, re-assembly and recyclability are essential.