Rapid-Cure Liquid Shim

Liquid shims are filled viscous resins used in aerospace assembly processes to form high strength fillers that bridge the small gaps in joints to prevent stress concentrations. Unfortunately, current liquid shims cure slowly; it takes more than 8 hours until the parts can be handled and up to 7 days to reach full strength. This slow cure limits the production rate of the Joint Strike Fighter. This SBIR project will develop a liquid shim that achieves full cure in two hours. This product will allow assembly of shimmed joints in a single shift. The formulation developed in Phase I passes all the requirements tested to date for a liquid shim meeting AMS 3726C. In Phase II, TDA will optimize and scale up the manufacture of the curing agent and rapid-cure liquid shim formulation, assuring reproducible production. Batches will then be formulated and packaged into cartridges. The packaged shims will be tested to assure they will meet the specification and that they have sufficient shelf life, and then will be evaluated at a prime airframe manufacturer. At the end of Phase II, production will be well documented and routine, and that the new shims will be ready for qualification for aerospace assembly.