Bonded composite repair, consisting of a polymer composite patch bonded to a damaged part with an adhesive, is widely used to repair aerospace components. In current repair practice, any repair with cure temperature variation outside a very narrow band must be reworked and sometimes rejected even though the repaired part might be acceptable for service.

Furthermore, the cure state throughout the repair patch and the bondline is not known; therefore, an accurate estimation of the mechanical properties during cure is not possible. Moreover, the current practice relies heavily on thermocouples for monitoring the quality of repair. However, thermocouples are prone to failure, could compromise vacuum bag seal, and their use is limited to measuring temperature on the outmost layer of the repair patch and not at the bondline or inside the patch.

To address these shortcomings, a new approach utilizing an encapsulated-sample rheometer and micro-size wireless temperature sensors (microwires) is proposed to perform cure management of bonded composite repair. Using the microwires, the temperature of the bondline and the repair patch at different thicknesses inside the material will be measured during cure. The microwires will monitor temperature during cure without compromising the vacuum bag seal since their signal is wireless. The cure time-temperature data will be fed into viscosity models to determine the material state of the repair patch in realtime. Accordingly, the obtained complex viscosity will be mapped into a time-temperature-viscosity cure diagram to track the actual cure path and to estimate the final mechanical properties of material.

Utilizing a university-NASA-industry collaborative approach, this project will involve Wichita State University, Kansas State University, University of Kansas, and Emporia State University and it will be conducted in collaboration with NASA Langley and Glenn Research Centers, Lockheed Martin, Hawker Beechcraft, Spirit AeroSystems, Bombardier-Learjet, American Airlines, and National Institute for Aviation Research.