Non-destructive testing and detection of electro-thermal damage in carbon fibre reinforced composites under fault-representative conditions

The reliance of modern aircraft development on Carbon Fibre Reinforced Plastics (CFRP) composites amounts up to 50% of an aircraft’s total component structure offering high strength-to-weight ratio, corrosion resistance, and superior fatigue performance. The parallel integration of CFRP structures within more electrified aircraft architectures introduces new potential failure modes (Rail-to-ground and high-impedance fault conditions) associated with unintended electrical current flow through structural components. However, CFRP’s electrical response, consequent electrical degradation from joule heating and residual structural integrity is poorly understood, leading to over-engineered solutions ensuring that CFRP is kept separate from conducting channels. This research develops a diagnostic framework that integrates ultrasonic Non-Destructive Evaluation (NDE) and destructive mechanical tests, with varied electrical loading conditions for the 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 7 A, raising local temperatures to 20^oC below and above the glass transition temperature (T_g) of the polymer matrix. Real-time infrared thermography monitored temperature during conduction. Post-conduction Phased Array Ultrasonic Testing (PAUT) and micro-CT were deployed to assess thermal damage relative to T_g. Robotic PAUT was employed to acquire spatially registered volumetric data of CFRP, reconstructing time-resolved A-scans into B-scan slices and a 3D ultrasonic volume. These measurements were correlated with micro-CT, electrical resistance, destructive characterization, and visual observations. Initial NDE results indicate that ultrasonic methods are sensitive to early-stage subsurface degradation due to conduction of electrical fault current. Mechanical testing further confirms a reduction in interlaminar strength in affected regions.