Measurement and analysis of impact-induced strain using extrinsic Fabry-Perot fiber optic sensors

In-plane strain responses of surface-mounted extrinsic Fabry-Perot interferometric (EFPI) fiber optic strain sensors are investigated. EFPI fiber optic strain sensors are mounted on three graphite/epoxy laminated composite plates. The plates are impacted with various size steel balls using a drop-weight technique. The impacts did not cause apparent damage. The first impact-induced strain peak was characterized by the rise time, peak value, full width at half maximum and decay time. The transient low-velocity impact response of EFPI fiber optic strain sensors is compared to the response from conventional electrical resistance strain gages and polyvinylidene fluoride (PVDF) piezoelectric film sensors. Orientation dependence and other characteristics of the EFPI fiber optic sensing technique are discussed. An in-house finite element program incorporates geometric nonlinearity and transverse shear deformation for the impact events. The finite element results closely match the experimental strain data for the first peak strain response.