A quantitative parameter for non-destructive evaluation of drilled laminated composite parts

Composite materials usually undergo some form of intermediate processing such as adhesive bonding and drilling before achieving their final product form. Such processing could affect the structural integrity of the final component. Thus, the ability to non-destructively evaluate the part after a machining operation, for example, is of great interest to the scientific community. A non-destructive ultrasonic C-scan technique is traditionally utilized to qualitatively evaluate composite panels. This technique presently involves human interpretation of color images obtained from the C-scan system. The ability to eliminate human involvement and to obtain a consistent quantitative evaluation of the part is desirable. This paper discusses the development of a damage-sensitive parameter based on the gray-scale data of the C-scan image and relates this parameter to the extent of changes in the structural integrity of composite laminates due to a drilling operation. The behavior of the parameter compares well with the measured results.