Non-destructive testing methods to quantify joule heating induced degradation in carbon fibre reinforced polymers

Carbon-Fibre Reinforced Plastic (CFRP) composites are extensively used for modern aerospace structures for their high strength-to-weight ratio and corrosion resistance. A parallel technology supporting decarbonisation of aviation is increased electrification of power and propulsion systems. However, due to its poorly understood electrical response, and associated mechanical degradation from Joule heating, systems design ensures that CFRP structures do not conduct electrical current. This leads to over-engineered solutions. This research develops a diagnostic framework that integrates ultrasonic Non-Destructive Evaluation (NDE) with varied electrical loading conditions for the early detection and characterization of electrical degradation in aerospace-grade CFRP. In this study, quasi-isotropic carbon-fibre/epoxy laminates were subjected to controlled electrical currents of up to 5 A, raising local temperatures to 30oC, 20oC, and 10oC below and above the glass transition temperature (Tg), of the polymer matrix. Real-time infrared thermography monitors temperature during conduction. Post-conduction phased array ultrasonic testing assesses thermal damage relative to Tg. Phased array ultrasonic testing enables waveform features from A, B and C scans to be correlated with internal damage and conductivity, non-contact, and non-destructive characterization. Visual changes and changes in electrical properties. Initial NDE results indicate threshold temperatures and associated current levels for delamination.