Robustness of embedded fibre optic sensor mesh configurations for monitoring composite structures

Abstract

Fibre optic sensors are attractive for monitoring of composite structures but the significant risk of damage to fibres where they enter the structure and within the structure itself can make their use unreliable. Mesh configurations of embedded fibre Bragg grating sensors with improved robustness are considered for monitoring composite structures. The configurations of single ended line, bidirectional line, loop, and a novel 2×2 mesh are analysed using a probabilistic model of the sensor system robustness. Numerical evaluation of these configurations has shown that the 2×2 mesh configuration provides the greatest robustness of all of the configurations across all inlet port failure probabilities. The probability of a sensor becoming isolated in a 2×2 mesh is approximately 3 times lower than for the bidirectional line configuration. Using a new matrix approach, the 2×2 mesh configuration is analysed in terms of disaggregation of individual sensor spectra for both fault free and faulty conditions. Simulation and experimental evaluation have demonstrated that successful recovery of individual grating spectra is possible with small spurious signals.