This paper describes the application of infrared thermography combined with microwave excitation to detect bonding defects in a carbon fiber reinforced concrete structure. Electromagnetic and thermal phenomena are modelled and compared with experiment. Several short-term tests have been carried out using both continuous and pulsed excitations. They showed that the detection of this type of defects by this method is effective.

The induction heating using a circular coil in Carbon Fiber Reinforced Polymer (CFRP) laminates produces unique heating patterns, significantly influenced by the fiber orientations in each layer and electrical contacts between layers. This study investigates these patterns using thermography and reveals a transition from circular to rectangular heating patterns under the influence of a circular induction coil. This shift is driven by changes in interlaminar microstructure, particularly increasing fiber separation at interfaces, interpreted as fewer electrical contacts. The research also presents a novel nondestructive, non-contact method for identifying fiber orientations within CFRP laminates. The method employs a 2D Fast Fourier Transform (2D-FFT) to extract fiber orientations from the spatial characteristics of the heating patterns. The study demonstrates the effectiveness of this method for accurately determining fiber orientations in quasi-isotropic CFRP laminates. This methodology opens potential applications for large-area inspection and quality control in fiber-reinforced composite manufacturing.