Evaluation of revealing and quantifying techniques available for drilling delamination in woven carbon fiber-reinforced composite laminates

Abstract

Delamination is the major defect for drilling of composite laminates. There exist different nondestructive tests (NDTs) to reveal delaminated zone, including digital photography, X-ray CT scanning, and ultrasonic C-Scan. Different delamination factors were presented to quantify delamination extension. In this paper, some difficulties regarding revealing damaged zone in drilling of woven carbon fiber-reinforced plastics laminates are discussed. In addition, different NDTs as well as available delamination factors are examined. For NDTs, clarity of pictures, applicability, and reliability are compared to help researchers select proper option. The result of this study demonstrates that compare to other available factors, the adjusted delamination factor F_da varies in wider ranges in normal engineering applications. It is less sensitive to the implemented NDT and it presents different values for different delamination extension patterns. Therefore, pattern-sensitive factor F_da is more suitable to quantify damaged zone. However, for cases with low circularity parameter f, like drilling of unidirectional composite laminates with extended damaged zone, F_da may be replaced by easily measured diameter delamination factor F_d.