Parameters impact analysis of CFRP defect detection system based on line laser scanning thermography

Carbon fibre reinforced polymer (CFRP) plays an increasingly important role in many fields, and the non-destructive testing (NDT) for its defects is drawing more and more attention. In this paper, a finite element model is established and the surface temperature difference between the defective and non-defective areas is selected as the characteristic quantity to systematically study the impact of three parameters, such as scanning direction, laser power and scanning speed, on the detection effect in the line laser scanning thermography NDT system. Qualitatively, the scanning direction is consistent with the carbon fibre orientation, the higher the laser power, and the slower the scanning speed is, the more favourable the defect detection. Further, the data obtained from the simulation are fitted, and the results show that the scanning speed and laser power have exponential and linear relationships with the maximum temperature difference, respectively. A related experimental system was established, the laser power was set to 7-, 10-, 13- and 15 W as well as the scanning speed to 10-,20-, 40- and 50 mm/s, to investigate the temperature variation of CFRP specimens containing artificial defects. The experimental results show that a greater laser power or lower scanning speed can obtain better defect detection compared with a smaller power or higher scanning speed.