Monitoring of the curing process of composite structures by tunnelling junction sensors

• The use of quantum phenomenon called the “tunnelling effect” for monitoring temperature variations.
• The use of Low Pressure Chemical Vapour Deposition for manufacturing tunnelling junction sensors.
• The embedding of a tunnelling junction sensor inside a carbon–epoxy composite plate to track temperature during its curing process.
• The adequate performance of tunnelling junction sensor to respond to temperature variations during the composite curing process.

In this work, tunnelling junction sensors (TJS) are proposed for monitoring the curing of Carbon Fibre Reinforced Plastic (CFRP). Tunnelling junction sensors are very sensitive to temperature changes; therefore they are suitable for this application. TJS are manufactured by Low-Pressure Chemical Vapour Deposition (LPCVD) and electronically characterized to obtain their V(I) diagram. One sensor is embedded on a carbon–epoxy plate for measuring temperature evolution during composite’s autoclave cycle. By means of a temperature–voltage–time curve, the evolution of sensor’s signal related to temperature changes can be tracked. The main goals are to verify the viability to apply this technology to composite’s curing process and to provide a first approach of the initial state of the composite plate by verifying the temperatures at each curing stage. Both purposes were achieved and help to better understand the composite polymerization process, which has a strong influence on the composite’s mechanical performance.