Laser–Ultrasonic Study of Local Porosity Distribution in Carbon Fiber Reinforced Plastic Stringer Panels

A method for quantitative evaluation of the porosity in carbon fiber reinforced plastic (CFRP) structures based on laser excitation of probe ultrasonic pulses is presented. The technique of estimating the porosity level in a material has been proposed using the experimentally measured phase velocity of longitudinal acoustic waves propagating in this material. By the example of control samples and actual CFRP structures, the possibility of obtaining maps of the local porosity distribution in the studied region of the structure has been demonstrated. It has been shown that in the structures studied, there are regions with a significant variation in the local porosity level. The proposed method can be used for quality monitoring of manufactured composite structures, as well as for studying the structural changes during operation of the structure.