A Fiber Optic Strain And Impact Sensor System For Composite Materials

Abstract

An elliptical core two-mode fiber can be used as an effective fiber sensor, due to the fact that interference between the LP01 and LP11 modes in an elliptical core fiber is sensitive to perturbations in the surrounding environment. A fiber optic sensor system using an elliptical core two-mode fiber has been developed for measuring strain and impact damage in composite materials. Various elliptical core fibers have been embedded in composite materials and the effects of the embedding process on the fibers have been investigated. The strain measurement was calibrated by measuring the beatlength of the two-mode fiber after embedding. Impact damage detection was performed by measuring the acoustic impact waves propagating in the composite material. The sensor system employs a laser diode whose wavelength can be adjusted to correct the offset of each individual sensor. The experimental results demonstrate the feasibility of using two-mode fiber optic sensors for measuring strain and detecting damage in composite materials.