Comparison of X-ray Computed Tomography and Ultrasonic C-Scan Techniques and Numerical Modelling of Impact Damage in a CFRP Composite Laminate

Two different experimental techniques are employed to visualize the impact damage generated by a low-velocity impact on a carbon-fibre reinforced-polymer (CFRP) composite laminate. At the relatively low impact-velocity of 1.69 m.s-1, and a corresponding impact energy of 7.5 J, used in the present work the damage induced in the CFRP panel is barely visible to the naked eye but the techniques of ultrasonic C-scan and X-ray computed tomography (CT) can detect the damage that has occurred. This damage is mostly interlaminar damage, i.e. delaminations, between the plies due to a change in modulus from one ply to the next in the laminate. This interlaminar damage is usually accompanied by intralaminar damage, e.g. matrix cracking, in the ply itself. The type and extent of damage detected from using these two techniques is discussed and the relative merits of these techniques are compared. In general, the CT gave the better resolved picture of damage but the lateral extent of the damage was underestimated relative to C-scan which was more sensitive to very fine delamination cracks. In addition, a numerical approach, based on a finite-element analysis model, is employed to predict the type, location and extent of damage generated by the impact event and the modelling predictions are compared to the experimental results.