Depth-size 2D quantitative delamination defect identification method in GFRP using constant temperature excitation transmission infrared thermography

At present, the widely used Glass-Fibre-Reinforced Polymer (GFRP) materials have limited performance due to their susceptibility to defects during production and use.Focusing on the continuous detection process of composite materials, this study addresses the challenge of delamination defects in GFRP during manufacturing and service by proposing a depth-size 2D quantitative defect identification method using constant temperature excitation transmission infrared thermography. Through the comprehensive analysis of thermograms and temperature curves, a quantitative identification method for the depth and size of defects in GFRP laminates is obtained. With a defect depth of 2 mm and a defect size of 14 mm, average relative error (ARE) can reach 4.79% and 5.58%, and coefficient of variation (CV) can reach 4.56% and 5.42%. Except for the defect depth of 8 mm and the defect size of 4 mm, the ARE and CV of all other groups are below 15.00%. Due to the use of constant temperature excitation method, this identification method is highly suitable for continuous detection compared to other periodic or pulsed excitation methods. This method will greatly improve the defect detection efficiency of infrared thermography (IRT) in GFRP materials. And it can make an important contribution to the quality control of GFRP materials.