Non Contact Ultrasonic Techniques for Composite Material Diagnostics in Aeronautics Applications

摘要

The aim of this paper is to check the potential of "one side" non contact ultrasonic techniques with respect to the transmission configuration, in order to improve the accessibility of the inspection, e.g. on installed components, without decreasing its resolution and accuracy. To this purpose the following ultrasonic transducer configurations have been considered: transmission, pitch & catch and delta. They have been applied to composite materials for aeronautics applications, in order to identify defects and flaws. Carbon Fiber Reinforced Polymer (CFRP) panel and honeycomb specimens for aeronautic applications have been studied. Two different ultrasonic systems are analysed in this paper, based on electrocapacitive and piezoelectric probes respectively. A scanning frame has been realized in order to place the various types of transducers in the different configurations with a fine adjustments of their position and orientation. Delta configuration has been here investigated for the first time (to the author's knowledge) using non contact probes. Potentials and performance of the studied techniques have been evaluated in terms of Signal to Noise Ratio (SNR) and defect identification capabilities. Furthermore, an experimental parametric study has been performed in order to define the optimal set-up of the measurement chain, in particular concerning the probe positions. Moreover this work leads to discuss about limits and breakthroughs of non contact ultrasonic techniques and their effective implementation for industrial applications.