Ultrasonic Detection of Damage in CFRPs

Abstract

A good knowledge on damage processes in CFRPs can be given by developing non-destructive testing. In order to improve ultrasonic capabilities to detect matrix cracking development, a water tank has been mounted directly on a servo-controlled machine and an automatic scanning by points has been investigated. More accurate testing procedures have been implemented including mechanical improvements, amplitude measurement accuracy, resetting points under loading, comparative evaluation of the attenuation between undamaged and damaged state. A comparison between X-ray and ultrasonic results has been made. Another aim was to control hidden damage due to impact and especially to measure the size and shape of delaminations at each interply location using an improved pulse echo method. Hence, conventional equipment has been modified in order to explore the material by thickness segments. A new procedure has been added to a classical equipment providing in a single scan multiple C-scan images of a coupon with a very limited amount of data. The main purpose of this paper is to describe the methods used and to discuss the original procedures that have been performed. The new capabilities of an improved ultrasonic set-up are going to be examined mainly in relation to crack-density measurement, matrix cracking development under tension and ply by ply delamination sizing and location. With these features, an ultrasonic set-up can find its application in many aeronautical fields: improving composites, moisture influence on damage, detecting of damage resulting from impact, structures lifetime.