Employment of active thermography for nondestructive evaluation of different defect types in carbon fiber reinforced polymer composite panels with flat and curved geometry

Recently,the use of fiber-reinforced polymers has become widely used in various industries. Carbon fiber reinforced polymers (CFRP) are widely used in the aerospace, nuclear, renewable energy, architecture, and marine industries. The complexity of the manufacturing process of these parts is always associated with the formation of various types of manufacturing defects. The existence of non-homogeneous structure in these parts has faced several limitations in the use of classical NDT methods in the inspection process. The active thermography method using infrared waves is today considered as one of the proposed methods in the inspection of composites. In the present work, samples with flat sheet geometry and curve sheet geometry of carbon fiber-reinforced polymer were tested using a pulse technique. Several different types of defects with different dimensions were manually created in these parts and inspection was performed using the thermography method. The results have shown that the use of radiant thermal stimulation with the transmission technique can well reveal the internal defects of the samples. The presence of different thermal conductivity of needle-shaped metal defects with 0.2 mm diameter, foreign particles with 2 mm diameter, and 10×10 mm2 delamination led to the appearance of these defects in flat and curved samples.