VISUAL DETECTABILITY OF BLUNT IMPACT DAMAGE IN A STRINGER-STIFFENED CFRP FUSELAGE PANEL

Abstract

The influence of inspection parameters on the detectability of damages has been determined by visual inspections producing 112 inspection records. Two nominally equal structures, with nominally equal impact damages have been manufactured, so inspection results for both structures could be compared to each other. Both structures were exposed to different inspection conditions (surface colour/finish, illumination, cleanliness, inspection angle), thus enabling the determination of influences of single inspection parameters on the detectability of damages. By collecting anonymous personal data of the inspectors it was also possible to evaluate the influence of professional qualification, visual capability, age and gender of the inspectors on inspection results. Comparing the internal damage as it was detected by ultrasonic scanning for impact energies of 40 – 75 Joule, damage areas caused by the blunt impacts were in the same category as damage areas caused by 25.4 mm diameter impactors of the same energy. While impacts from small diameter impactors caused a visible dent, which was not difficult to detect by a careful visual inspection, the flat, spread out dents from blunt impactors were often overlooked.