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 fiber optic sensors. Fiber 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 fiber 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.

FBG-based monitoring of solidification strain development in a microstereolithography photocurable resin

“…Many scientific works utilizing FBG sensors for in situ material/structure cure monitoring have been reported. For example, fiber Bragg sensors (FBG) have been used for simultaneous monitoring of the fabrication strain and the cure temperature in fiber reinforced composites (Chehura et al, 2005;Kang et al, 2003;Montanini and D'Acquisto, 2007;O'Dwyer et al, 1998). A single embedded FBG sensor within an epoxy resin, placed into a rectangular mold, was implemented to detect on-line the resin gelification onset and the strain build evolution during the whole non-isothermal cure cycle (Antonucci et al, 2006).…”

Process monitoring of fibre reinforced composites using a multi-measurand fibre-optic sensor

“…The crosstalk was not found to be significant with the measurement technique that was used. Kang et al [23] used a similar sensor design previously reported by Liu et al [22] to monitor the strain and temperature of unsymmetrical composites. Ferreira et al [24] decoupled the FBG signal from the combined EFPI and FBG signals by passing the signal through a Bragg grating that was similar to that used within the sensor-head.…”

Monitoring Manufacturing of Composites Using Embedded Distributed Optical Fibre Sensors

“…Strain gages, amongst other sensors, had been largely employed to monitor the curing stages in the fabrication of FRP components and, in the last 20 years, optical fibre sensors (OFSs) had been incorporated to provide a non-invasive in situ channel to track in real time the composites' behaviour while being manufactured and even after at operational conditions [1,2,[4][5][6][7][8][9]. Despite the employment of either strain gages or OFSs (fibre Bragg grating or extrinsic Fabry-Pérot interferometric sensors) for cure monitoring [10], the information obtained from these sensors is only punctual and cannot cover a larger sensing region.…”