Full 3D characterisation of composite laminates using ultrasonic analytic signals

Driven by environmental targets on CO2 emissions, the aerospace and automotive industries are designing lighter structures with composites and are requiring much higher fidelity non-destructive information about the internal structure of manufactured composite components. Consistent research progress over the last decade has gradually revealed a wealth of detailed information within the ultrasonic pulse-echo response from composite laminates. Unlocking that information requires careful treatment of various unwanted effects such as phononic band gaps and phase singularities in the data, followed by inversion methods to convert the ultrasonic data into three-dimensional maps of actual material properties, such as ply-location maps, out-of-plane ply-angle maps and in-plane fibre-orientation maps. From these, any tape gaps and overlaps can be tracked and deviations from the design such as wrinkles can be quantified. This paper presents each stage in the state-of-the-art processes developed by the authors and applies them to real composite specimens.