Low energy impact damage monitoring of composites using dynamic strain signals from FBG sensors – Part II: Damage identification

In part I of this two-paper series, a method for the localization of an impact using dynamic strain signals from fiber Bragg grating (FBG) sensors is presented. In this paper, an inverse numerical–experimental method allowing to identify the damage based on experimentally measured eigenfrequency changes is developed and validated. The damage identification is limited to a region in the vicinity of the impact position predicted by the localization method. The eigenfrequency changes are determined experimentally from dynamic strain signals obtained with embedded FBG sensors and the parameters of a homogenized damage model are adjusted to fit the numerical results to the experimental data.

► Inverse numerical–experimental method for identifying damage size and position.
► The criteria are the eigenfrequency changes due to damage determined by FBG sensors.
► The damage model includes damage factors reducing the transverse shear moduli.
► In experimental examples an accuracy better than 30% is found for the damage size.