High-Strength, Conductive Adhesives a Sticky Proposition Published Aug. 30, 2010 By Max Alexander Materials and Manufacturing WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- Air Force Research Laboratory Small Business Innovation Research resourcefulness is behind new adhesives promising increased performance and substantial cost savings for a wide variety of Air Force and Department of Defense air and space platforms. Specifically, the SBIR Phase II work--performed by Luna Innovations--produced high-strength aerospace adhesives supplying continuous electrical conductivity and thus addressing the military's need for bonding agents that are not only strong, but also able to mitigate electrostatic discharge, on aircraft/spacecraft surfaces, facilitate electromagnetic interference shielding, and protect craft from lightning strikes. Applications demanding a combination of high-strength structural joining and increased electrical conductivity will benefit from leveraging the new adhesives as bond and/or filler materials. Further, by reducing--and, in some cases, eliminating--the need to outfit structures with costly electrical materials in addition to complex ESD, EMI, and LS mitigation mechanisms, the single-package technology could save the AF and DoD millions of dollars annually. The capacity to maintain continuous electrical conductivity across an aircraft/spacecraft surface is crucial for meeting the comprehensive electrical and mechanical requirements of the particular system. At joints, gaps, and bolt holes, this is difficult at best, with current solutions entailing both an electrical bridging component (e.g., an adhesive or wire mesh) and a structural adhesive. Unfortunately, these components result in high costs, extra weight, and configuration complexity. To address these issues, Luna adopted a novel approach--one involving the careful selection and dispersion of conductive fillers within high-performance adhesive resins. This process creates conductive adhesives with pot life (working life), cure time, and application and mechanical properties similar to those of the products presently used by the military, commercial aircraft manufacturers, and maintainers. The adhesives have undergone characterization for determining their performance properties, including bond resistance, volume resistivity, shielding effectiveness, lap shear strength, out-gassing characteristics, and other metrics that serve to define end-use applications. Results indicate that Luna's adhesives have tailorable mechanical and electrical properties; for example, the company has developed adhesive formulations exhibiting lap shear strengths of 4,500 lbs/in2 and electrical resistance of <0.1 Ω across the bond. This tailorability promotes increased design flexibility and assembly speed, adding to already-noted advantages in terms of enhanced system performance and reduced costs, weight, and complexity.