New Technology to Find Flaws in Aerospace Composites

Headed up by QinetiQ, the UK consortium of Southampton University and the University College London along with four companies in ProjectCAN brings together leaders from academia, aerospace and X-ray equipment manufacture.

As part of the government’s Aerospace Technology Institute, Innovate UK, the agency has provided the team with a large amount of funding to develop two new non-destructive testing processes for the detection of flaws in composite aerospace components.

The University of Southampton’s µ-VIS Centre for Computed Tomography is to host the first part of this three year project. Along with Nikon Metrology UK it aims to create and test methods for scanning and visualising the inside of large, flat composite components using X-rays. The team will create both the system for acquiring the scan data and the software to rebuild it into a 3D volume image, allowing for manipulation and visualisation.

Dr Thomas Blumensath, of the University of Southampton said;

Conventional computed tomography (CT) techniques are widely used but are not well suited to image extended flat objects. We will be developing an alternative technique, which applies computed laminography (CL) techniques, to overcome the limitations of conventional CT for large, flat components. This will enhance our ability to find defects in large composite parts, such as those which are increasingly used in modern aircraft.

Traditional computed tomography requires the scanned object to be fully rotated, and will only produce the best results when the X-ray attenuation for each angle is broadly similar. It is impossible to scan larger parts due to space restrictions and when scanning smaller flat panels, the variation of attenuation across the angles can become too large for optimal imaging. Computed laminography on the other hand, uses a different motion, such such as linear translation or limited-angle rotation, to scan components where computed tomography is impossible.

A laminography system has the hardware that positions the sample, source and detector to acquire 2D projection data, as well as an algorithm to reconstruct a 3D volume image from the data. ProjectCAN will develop both this hardware and software to allow laminographic imaging within the custom Nikon Metrology 225/450kV X-ray scanner already in service in the µ-VIS centre at Southampton.

At the same time, the team at Axi-Tek and the University college London will be developing a new backscatter x-ray inspection technique to inspect large areas of composite structures such as wing sections, engine cowlings and fuselage components. Backscatter will let the x-ray investigate the structural integrity of the composite materials from a single side of the component. To enhance this technique, the team also intend to combine the backscatter x-ray with more conventional optical surface inspection.