Comparison between Microwave Infrared Thermography and CO₂ Laser Infrared Thermography in Defect Detection in Applications with CFRP

Abstract

This paper presents two infrared thermography methods with CO 2 Laser excitation and microwave excitation applied to defect detection in CFRP. The tests were conducted with two specimens, one with defect, and another one without de fect. On two concrete plates 40 cm × 40 cm × 4.5 cmwere reinforced by CFRP; the defects were made by the absence of adhesive on an area10 cm × 10 cm. The specimens were heated by microwave, generated by a commercial magne tron of 2.45 GHz and guided by a pyramidal horn antenna, with a power of 360 W within 150 s. Another series of the tests w as conducted with CO 2 Laser, wavelength 10.6 μm, by heating the samples with a power of 300 W within 40 s. An infrared camera sensitive to medium waves in range of 3 - 5 μm, with a detector of 320 × 256 matrix detector in InSb (Indium Antimonide), was used to record the thermograms. As a result, the CO 2 Laser excitation is better for the delamination detection in CFRP. This study opens interesting perspectives for inspecting other types of defects in mate rials sciences; the microwave excitation is suitable for the deep defects in the materials whereas the CO 2 Laser excita tion is better for the defects near the surface of the materials .