Detection of damage in a rotating glass fibre-reinforced polymer disc using swept-source optical coherence tomography

Glass fibre-reinforced polymer composites exhibit attractive properties, such as a high strength-to-weight ratio. They can also be customized through manufacturing conditions and composition. However, to ensure reliability, measurement testing under realistic conditions is essential. A swept-source optical coherence tomography (OCT) system was used to evaluate the development of the damage behaviour of a polar-orthotropically reinforced multi-layered composite rotor in situ under rotational loading conditions. The experiment was carried out at various rotational velocities up to 165 rotations per second, corresponding to a linear speed of 259.2ms-1 at the outer edge of the rotor. The 3-dimensional data enable studying of the rotor’s textile architecture, in-plane and out-of-plane deformations as well as the crack growth over the entire accessible disc volume up to a depth of 2.5mm even at the highest applied rotational speeds. In contrast to previous OCT investigations conducted on stationary composite structures, this study demonstrated that this method is also suitable for acquiring volumetric images of fast-moving objects. This is important because the increasing radial loads resulting from higher rotation frequency are incorporated into reliability studies. Unlike OCT, other in situ measurement methods, such as Doppler distance sensors, diffraction grating sensors, and strain gauges, do not provide direct information about the inner material structure of the rotor. Furthermore, the work demonstrates that OCT can detect thin cracks and polyester threads not resolvable by computer tomography, another 3-dimensional imaging technique. Consequently, swept-source optical coherence tomography may be used to enhance the understanding and modelling of the damage behaviour of composite materials under load.