Simultaneous monitoring of strain and temperature during and after cure of unsymmetric composite laminate using fibre-optic sensors

Abstract

In this paper, we present a simultaneous measurement of strain and temperature during and after cure of unsymmetric cross-ply composite laminate using fibre-optic sensors. Fibre Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors are used to measure those measurands. The characteristic matrix of the sensor is derived analytically and measurements can be done without sensor calibration experiments. A wavelength-swept fibre laser is utilized as a light source. Two FBG/EFPI hybrid sensors are embedded in a graphite/epoxy unsymmetric cross-ply composite laminate in different directions and different locations. We perform the real-time measurement of fabrication strains and temperatures at two points within the composite laminate during the cure process in an autoclave. Also, the thermal strains and temperatures of the fabricated unsymmetric laminate are measured afterward in a thermal chamber. Through these experiments, FBG/EFPI sensors are proven to be an efficient choice for smart monitoring of composite structures.