Silicon Photonic Sensors, Embedded in Composite Tools, for the Optimization of Composite Aerostructure Production

Carbon fiber reinforced composites have become a staple in the aerospace industry, owing to their mechanical properties (low weight and mechanical stability). Resin Transfer Molding (RTM) is a manufacturing process for composite materials, offering significant cost reduction, compared to autoclave processes. To achieve the desired quality though, strict control of several process conditions is required. Monitoring the temperature and pressure conditions inside the tool along with the resin’s refractive index (monitoring its cure state), can provide tight control over the curing cycle. Leveraging Silicon photonics advantages (electrically passive and stable at high temperatures) can enable accurate tracking of the resin curing conditions. In this work, the first demonstration of silicon photonic sensors in the production of composite parts is presented. The sensors’ high thermooptic sensitivity (78.4 pm/°C) and linearity (0.9787) are leveraged, while being deployed inside a multi-ton composite tool. The devices are demonstrated under demanding temperature (up to 165 °C) and pressure (7 bar) conditions, during a 6-hour production cycle, compatible with an RTM-6 (aerospace-grade RTM) process. It shows highly stable performance across the full dynamic range (30-165 °C), accurately monitoring the cure state of the resin.