Automated quality assurance of CFRP-components using air-coupled ultrasound

Abstract

To this day, carbon fiber reinforced plastic (CFRP)-components are used in aerospace only to a minor degree, because its fabrication is much more expensive than production of metallic components, which is due to the high amount of handcraft that is involved. Therefore, it is the aim of the German Aerospace Center to automate the production process of CFRP by using robots. An important part of the production process is quality assurance. One of the methods that are used at DLR is non-destructive inspection (NDI) by using air-coupled ultrasonic testing (ACU-testing). In contrast to water-coupled ultrasonic testing, this method is completely contactless and allows for inspection of CFRP-components with high amount of porosity of a few percent. ACU-testing is going to be automated as well and, in another effort, be integrated into the automated production process. The acquired data from ACU-testing could then be used for optimization of the production process. Despite its high potential as an NDI-method, ACU-testing facilities for reflection measurements exist only in laboratories. Thus, it is another aim of DLR to improve the method to a degree, where it can be introduced into industrial sites. For this purpose, reflection measurements on test components and a pressure vessel were carried out with an ACU-testing device. In the course of those experiments the degree of automation of the NDI-method was increased step by step.