Improving the Structural Assessment of Aerospace Composites Using Non-Destructive Evaluation Based Models

Carbon-fibre composite materials are now widely used in the aerospace industry for their superior specific strength relative to the metals that they have replaced. But this class of material is highly sensitive to defects that typically have no visible presence on the material surface but cause substantial reductions in mechanical strength. One such defect is fibre-waviness, where the fibres in the composite are locally misaligned into a wave shape. To locate areas of fibre-waviness non-destructive evaluation techniques are used, these result in large amounts of image data which contain information about the defect. However, once this data is obtained, the processing and utilisation is often simplistic, resulting in all but the most basic characteristics of the defect being discarded. This leads to high levels of uncertainty in the strength predictions and thus structures often unnecessarily repaired increasing the operation costs.

The proposed PhD project will develop a new methodology for predicting the failure of defective composite components that contain fibre-waviness defects. This will be achieved by utilising as much of the image data that can be derived from ultrasonic non-destructive evaluation as possible, as well as using full-field measurements of surface strain. This experimental data will then be used as the input for finite element models that could be used to predict the performance of defective aerospace components under a range of different loading scenarios. The efficacy of using these models in industry will be demonstrated by quantitatively comparing the predicted behaviour with experimental surface strain-fields measured for the same load scenarios.

Applicants must have a good MSc or MEng degree in engineering, physics or an associated field. It is expected the successful student will spend equal periods of time at NTHU and UoL.