Vibration-based characterization of impact induced delamination in composite plates using embedded FBG sensors and numerical modelling

Dynamic strain signals from embedded fiber Bragg grating sensors are used for experimental modal analysis in carbon fiber reinforced polymer plates. Throughout a series of impact tests, the change of eigenfrequencies due to damage is evaluated for different impact energies. A detailed numerical model including the damage pattern obtained from X-ray computed tomography images demonstrates that most of the frequency changes can be explained by a delamination type of damage, whereas the total delamination surface has an affine relation to the absorbed impact energy. A homogenized damage model, including two damage factors, allows to predict the change of natural frequencies for a known damage size.