Abstract: In the drilling machining process of aeronautical carbon fiber composite laminate, layer defect is one of the most serious detections, which effects the connection of assembly and its using life. Ultrasonic phased array is widely used in detecting aeronautical composite defects because of its efficiency, flexiblity, intuitive display and so on. Aiming at improving the detection rate and imaging quality of drilling-induced delamination in composite laminates, this article mainly studied the effects of aperture, focal length and pulse width on results of detecting imaging by controlling variate method, then obtained the regular pattern of parameter changing and the most suitable install of each parameter. When the number of elements was too small, the focus beam length was too short. So it affects the detection rate of stratified defects and makes the defect information seriously distorted. With the number of elements under the same circumstances, the maximum amplitude of defect increased and then decreased with the depth of focus increasing. When the pulse width of the element excitation was about half of the center frequency, detection effect was optimal. This paper supplies reference to the following detection and study of drilling-induced delamination in composite laminates.

Key words: drilling layer defect, ultrasonic phased array, aperture, focal length, pulse width