Simultaneous measurement of strain and temperature during and after cure of unsymmetric composite laminate using fiber-optic sensors

In this paper, we use fiber-optic sensors and thermocouples to measure strain and temperature simultaneous during and after cure of unsymmetric cross-ply composite laminates. Fiber Bragg grating (FBG) strain sensor is used to measure strain, thermocouple is used to measure temperature. The characteristic matrix of the sensor is derived analytically and measurements can be done without sensor calibration experiments. A wavelength-swept fiber laser is utilized as a light source. Two FBG strain sensors and two thermocouples are embedded in a carbon/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 unsymmetric composite laminate during the cure process in hot press. Through these experiments, FBG hybrid sensors are proven to be an efficient choice for smart monitoring of composite structures.