SBIR-STTR Award

Fiber optic sensors offer the potential for measuring strain and monitoring the cure cycle and service life of filament wound composite motorcases provided that successful methods for embedding the fiber optic sensors can be developed. The proposed Phase I research program will investigate techniques for embedding fiber optic sensors in filament wound composite structures. A primary focus of this research will be to evaluate the effects of different optical fiber types, coating methods and sensor locations (i.e., orientation relative to composite ply directions) on the structural integrity of the composite. The feasibility of incorporating the fiber optic sensors into conventional filament winding processes will be evaluated. As part of the proposed research activity, analytical models will be developed to provide a methodology for evaluating the stress/strain stare for different fiber optic sensor configurations. Filament winding trials on simple cylindrical geometries will be conducted to assess fabrication feasibility. Final configurations will be selected for further demonstrated and testing in Phase II.

Keywords:
fiber optics filament wound structures composites embedded sensors rocket motorcases

Embedded fiber optic sensors offer unique opportunities for in-process monitoring, structural characterization, damage detection and service life monitoring of filament wound composite motorcase and launch tube structures. Before the application of such sensors can be realized, improved methods must be developed for embedding the fiber optic sensors during filament winding and interrogating the sensor response due to realistic loading conditions. As a result of the Phase I SBIR program, Technology Development Associates, Inc. (TDA) has demonstrated the feasibility of embedding Fiber Bragg Grating sensors into filament wound composite structures and has interrogated these sensors to measure internal strain metrics in the composite due to internal pressure loading. The proposed Phase II program will demonstrate the performance of the candidate Phase I processing methodology and sensor technologies for multiple sensors and combined loading conditions. Processing enhancements will be evaluated to automate the embedding procedure and locating optical fiber orientation. In order to meet the distributed strain and temperature sensing requirements, a combination of standard Bragg grating sensors, In-line Fiber Etalon (ILFE) sensors, and a new hybrid Bragg grating sensor technology are proposed. Multiplexing techniques will be used to make simultaneous measurements at several locations within filament wound pressure vessels. The primary application of the proposed research is for embedding fiber optic sensors in filament wound rocket motorcases and launch tubes to monitor cure cycle, measure strain/temperature during testing and/or monitor service life. Other applications for the proposed research include smart, lightweight composite structures for the automotive, ship, aircraft, spacecraft and sporting goods industries.