Method of Defect Detection of Thin CFRP Plate Using Sound Pressure With Electromagnetic Force Vibration

Carbon fiber reinforced plastic (CFRP) is a lightweight, high-strength material that takes advantage of the characteristics of carbon fiber and resin. CFRP is widely used in parts that require high strength, such as aircraft and hydrogen tanks. Although it has high strength, receiving a large impact may case delamination. The detection of these delamination is important for the strength and quality assurance of CFRP materials. In this research, the method of detecting the hole defect simulating back surface delamination with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\phi 6.35$ </tex-math></inline-formula> mm and depth 0.14 mm within 1.5 mm thick CFRP plate used in aircraft using electromagnetic force vibration due to the Lorentz force and measuring sound pressure was proposed. In this method, the CFRP material is vibrated using an electromagnetic force vibrator due to the Lorentz force, the vibration is converted into sound pressure and measured using a condenser microphone, and the location of the back surface delamination is identified from the signal strength. When the proposed inspection method is applied to a thin CFRP plate with the back surface delamination, since the vibration intensity at the back surface delamination location is increased, the defect can be detected. The method’s effectiveness was evaluated through experiments and the electromagnetic field displacement analysis using the 3-D finite element method.