Abstract:
In 2050, Denmark would like to obtain all its energy from renewable resources. Wind turbines, which are crucial for this purpose, can provide more power the longer their blades. However, longer blades mean that the materials placed in the load bearing parts should withstand higher loads. In predicting the lifespan of a blade, it is crucial to accurately characterise the mechanical properties of these materials. These are highly related to the internal structure of the material right down to the micro and nano-scales.
Through X-ray computed tomography (CT) it is possible to observe the micro-structure of fibre composites, and its changes under external loading conditions. This thesis demonstrates that, if X-ray CT is combined with the developed automatic image analysis pipelines, it is possible to automatically measure fibre geometry to a high degree of accuracy. From the measured fibre positions and diameters, it is possible to quantify parameters such as fibre misalignment, fibre volume fraction or distribution of fibre diameters. These can be related to the macroscopic behaviour of the material, as well as provide insights on the fibre manufacturing process.
This thesis demonstrates the precision to which fibre geometry can be characterised through X-ray CT combined with the developed image analysis tools. Measuring and tracking the changes in fibre geometry with high spatial and temporal resolution can aid the investigation of the very complex damage mechanisms that affect fibre composites under real-life loading conditions. For the first time, we were able to accurately follow how each individual fibre bends under compression loading of a composite, and we found that fibres start to tilt at very low loads and in a direction which is related to the final damage.
Read more about this thesis in DTU Orbit.
Principal Supervisor: Associate Professor Anders Bjorholm Dahl, DTU Compute
Co-supervisor: Professor Emeritus Knut Conradsen, DTU Compute
Examiners:
Associate Professor Jakob Andreas Bærentzen, DTU Compute (chairman)
Associate Professor Dan Witzner Hansen, IT-Universitetet, Copenhagen
Associate Professor Natasa Sladoje, Uppsala University, Sweden
Chairperson at defence:
Associate Professor Jeppe Revall Frisvad, DTU Compute
A copy of the PhD thesis is available for reading at the department
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