A novel IR-SRGAN assisted super-resolution evaluation of photothermal coherence tomography for impact damage in toughened thermoplastic CFRP laminates under room and low temperature

Evaluating impact-induced damage in composite materials under varying temperature conditions is essential for ensuring structural integrity and reliable performance in aerospace, polar, and other extreme-environment applications. As matrix brittleness increases at low temperatures, damage mechanisms shift: impact events that produce only minor delaminations at ambient conditions can trigger extensive matrix cracking, fiber/matrix debonding, or interfacial failure under severe cold loads, thereby degrading residual strength and fatigue life. Precision detection and quantification of subsurface damage features (e.g., delamination area, crack morphology, interface separation) are critical for subsequent mechanical characterization and life prediction. In this study, infrared thermography (IRT) coupled with a newly developed frequency multiplexed photothermal correlation tomography (FM-PCT) is employed to capture three-dimensional subsurface damage signatures with depth resolution approaching that of X-ray micro-computed tomography. However, the inherent limitations of IRT, including restricted frame rate and lateral thermal diffusion, reduce spatial resolution and thus the accuracy of damage size measurement. To address this, we develop a new transfer learning-based infrared super-resolution generative adversarial network (IR-SRGAN) that enhances both lateral and depth-resolved imaging fidelity based on limited thermographic datasets. • An IR-SRGAN based super-resolution infrared thermographic imaging system was introduced for the first time. • A three-dimensional photothermal coherence tomography method is introduced to reconstruct 3D subsurface structures in composite materials. • Three different toughened thermoplastic CFRP laminates under extremely low temperature and room temperature were subjected to different impact energy for observing the influence of temperature. • Various neat CFRP laminates and toughened CFRP laminates were tested to validate the measurement accuracy.