Embedding and testing of ultrahigh-sensitivity optical fiber sensors in prototype graphite composite spacecraft strut tubes

Ultrahigh sensitivity fiber cavity etalon (FCE) sensors have been embedded in graphite-reinforced polymer tubes fabricated by two different methods: resin transfer molding (RTM) and standard autoclave curing, and FCEs have been embedded in autoclave-cured unidirectional flat laminates. Significant issues encountered in embedding the sensors include protecting the fiber egress during layup, curing, and breakout, survival of the butt-coupled splice between the cavity and lead fiber during composite cure, maintaining sensor location, and sensor reliability and response. Methods were successfully devised to overcome these obstacles.