Ultrasonic Inspection Research Of CFRP Radius By Curved Array Probe

CFRP (Carbon Fiber Reinforced Plastic) has been increasingly used in aerospace. The geometrical shape of CFRP component also becomes more complex. However, internal defects will occur inevitably for CFRP component during its production and machining processes, especially for the radius part, which seriously degrades the performance of CFRP component. Phased array ultrasonic testing is promising for the inspection of CFRP due to its characteristics of beam controllability, high inspection efficiency, high precision and intuitive imaging. Compared with conventional linear array probe, curved array probe can geometrically focus at its circular center, which ensures normal incidence transmission of the ultrasonic field at any point of the radius surface, and therefore is more suitable for CFRP radius inspection. In this paper, simulation and experiment were both conducted for the investigation of detection ability of CFRP radius using curved array probe. The main conclusions are as follows:1. The metallographic microstructure of CFRP T-shaped component radius was analyzed, thus establishing its phased array ultrasonic inspection model. According to acoustic field simulation for linear array probe in CFRP plate, ultrasonic beam attenuation was serious when the incidence angle was large. Effective focusing and small attenuation occurred for normal incidence which was better for CFRP inspection;2. Numerical simulations on acoustic field and defect inspection for 5MHz curved array probe were studied under different parameters by use of the established model. Results show that:(1) for 4 elements aperture, pseudo-focus occurred, and the ultrasonic beam width lied in 1.5mm depth of radius narrowed and was almost invariant with focus depth; (2) When keeping the focus depth at a constant value of 25mm, the 3/4/5/6 elements aperture were selected for comparison. With the increase of aperture size, the ultrasonic beam energy increased, the length of the focal zone became shorter and the focusing capability became stronger. But, obvious ultrasonic beam split was also observed. So, the acoustic field for 4 elements aperture was better; (3) Defect sizing results presented little difference under different focus depth and apertures. Quantitative evaluation of the simulated defect show that the axial size and defects depth corresponded well with the actual value. But large deviation occurred for the circumferential sizing, and this was mainly due to the approximate process of that model. For the 0.5mm deep defects, defect and surface echoes overlapped and this could be improved through parameter optimization of testing frequency;3. Practical inspection of CFRP specimen radius with embedded artificial defects of varied axial size and depth was conducted using curved array probe. Quantitative evaluation of defect sizing and location matched well with the designed values under different focus depth and apertures. The defect depth results were basically same under different focus depth. The axial sizing and circumferential sizing results had a little deviation from the designed values. After 1.5mm deep defect with 3mm axial size and circumferential size was dissected, metallograph showed that ultrasonic results matched well with actual defect size and proved the ability of inspecting CFRP radius by curved array probe.