Low energy impact damage monitoring of composites using dynamic strain signals from FBG sensors – Part I: Impact detection and localization

Fiber reinforced composite materials risk to suffer from subsurface, barely visible, damage induced by transverse relatively low energy impacts. This two-paper series presents a method for the localization of an impact and identification of an eventual damage using dynamic strain signals from fiber Bragg grating (FBG) sensors. In this paper, the localization method allowing to predict the impact position based on interpolation of a reference data set is developed and validated. The data utilized in the method are the arrival times of the asymmetric zero order Lamb waves at the different sensors. A high rate interrogation method based on intensity modulation of the Bragg wavelength shift is used to acquire the FBG signals. The localization method allows to predict the impact position with a good accuracy and therefore the inspection of the laminate can be limited to this region.

► Localization of transverse impacts on fiber reinforced composite plates.
► Propagating waves are sensed using embedded and surface-glued fiber Bragg gratings.
► Interrogation rate of 1 GHz and threshold method to determine arrival times of waves.
► The impact location is predicted via interpolation within a reference data set.
► The accuracy depends on the signal’s noise level and is independent of plate size.