Automated analysis and advanced defect characterisation from ultrasonic scans of composites

With the rapidly escalating usage of composite materials, not only in military aircraft but in civil airliners as well, production NDT throughput is already stretched to its limit internationally. NDT data analysis is set to become the bottleneck preventing the required rise in production rates of composite civil aircraft in the next few years. Thus there is an argent requirement for rapid, automated analysis of up to a Terabyte of data per airliner; escalating to over 200 Terabytes per year - worldwide. The primary aim of automated analysis is to release operators from the time-consuming analysis of all scans and focus operator attention oil non-compliant structures. A secondary aim is to provide three-dimensional quantitative information that lightens the operators decision-making burden. Through advanced characterisation methods, NDT also has the potential to provide crucial feedback to control the composite production process, increase production yield and decrease costs. Current analysis methods for ultrasonic scans produce through-thickness average parameters, which provide little useful information to assist the stress analysis for defects, or the production process. Three-dimensional characterisation of defects call increase yield by informing the concession/disposition process for defects. For future process control., information is required about the 3D distribution of material properties in the structures on the production line, providing comprehensive long-term trend analysis. As well as demonstrating a new rapid automated analysis method for large-area ultrasonic scans, this paper proposes new ultrasonic methods for generating quantitative 3D profiles of porosity, resin layer thickness, ply spacing and fibre, orientation. Front these it is possible to determine play stacking sequence and measure in-plane fibre waviness and out-of-plane fibre wrinkling. Armed with these new tools there is the potential for solving the NDT data analysis bottleneck for composite aircraft. Examples are given of the use of these tools on carbon-fibre composite structures. Stacking sequence has been determined in structures up to 18 mm thick, and out-of-plane wrinkling measured in 35 nun-thick structures, although penetration depends on the measurement parameter, material quality and the ply, spacing. The tools are software based and are applied through post-processing of full-waveform data acquired using one of several suitable ultrasonic acquisition systems. These include commercially available phased array systems.