A simultaneous dual-parameter optical fibre single sensor embedded in a glass fibre/epoxy composite. (15th August 2021)

• Record Type: Journal Article
• Authors: Fazzi, Luigi; Valvano, Stefano; Alaimo, Andrea; Groves, Roger M.
• Is Part Of: Composite structures. Volume 270(2021)
• Publication Date: 2021-08-15
• Subjects: Fibre Bragg Grating -- Strain -- Temperature -- Dual-parameter sensor -- Composite -- FEM; Composite construction -- Periodicals; Composites -- Périodiques; 624.18
• DOI: 10.1016/j.compstruct.2021.114087
• Languages: English
• ISSNs: 0263-8223

Abstract

Highlights: Each single TFBG sensor can detect simultaneously temperature and strain variations. Any two resonance peaks in the spectrum can be used by the demodulation technique. Steady-state analysis of composite + optical fibre FEMs matches TFBG measurements. The accuracy of the TFBG can be increased by improving its thermal resolution. The thermomechanical state of a composite can be monitored by embedding a TFBG. Abstract: A simultaneous two-parameter single sensor based on weakly tilted Fibre Bragg Grating (TFBG), embedded in a 1 mm glass fibre/epoxy composite plate, is demonstrated to measure independently the temperature and strain variations induced in the material by the exposure to heating lamps. The spectrum of weakly TFBGs is composed of several peaks that can be used for different sensing purposes. Here, the shifting of the Bragg and the Ghost peaks are considered to calculate the strain and temperature variations through thermomechanical sensitivity coefficients of the selected peaks. To prove the reliability of the TFBG measurements, the resulting strain values were compared with the strain measurements obtained from the TFBG when compensated by a K-thermocouple embedded close to the optical fibre sensor. Furthermore, the numerical simulation of the full Finite Element Model (FEM) (composite + TFBG) and partial FEM (composite only) models were carried out by assuming a 3-D Gaussian temperature profile. This allowed the TFBG experimental measurements to be compared with the simulated results. A study focused on the strain deviation showed a good match between the full FEM and the TFBG measurements with an average error of ~5% in the case of the dual-parameter sensor and ~2% for the compensated TFBG.