Damage detection in a radome sandwich material with embedded fiber optic sensors

Abstract

Embedded distributed micro/macro-bending multimode optical fiber transducers multiplexed in the time domain (photon counting, optical time domain reflectometry) and quasi-distributed embedded in-fiber Bragg grating (FBG) filters based on wavelength measurement and demultiplexing encoding have been used for damage detection assessment in a radome sandwich structure. Both methods are well suited for detection and localization of permanent damage induced by impacts of energy ranging from 8-20 J. Optical fiber sensor measurements have been compared to those given by classical health monitoring methods using ultrasonics and shearography, as well as infrared thermography.

Application of the Piezoelectricity in an Active and Passive Health Monitoring System

“…In this case, the results demonstrated again a strong sensitivity of the three sensors R 6 , R 5 and R 4 to the damaging impact at 40J, as their passive damage indexes DI p were greater than 0.4. Moreover, a smaller variation of damage index DI A than in the preceding case was observed for the sensor R 6 . This revealed a lower sensitivity of the Lamb mode S 0 than the Lamb mode S 1 to the damage.…”

“…In this situation, the health monitoring system can be either local or global. For the local inspection, the sensor must be in the damaged region, registering permanent strains due to the damage [5][6]. For the global inspection, stimulations are produced in view to induce a structural response, analysed by the sensors.…”

Interaction between optical fibre sensors and matrix cracks in cross-ply GFRP laminates. Part 2: Crack detection

“…Equation (2) shows that when a polarimetric sensor is embedded in a cross-ply laminate, there is a linear relationship between the longitudinal strain applied to the coupon and the optical output phase change. This means that when the strain varies with time, the fringes induced by the change of strain will vary with time as well, as shown in Figure 3(a).…”

Long term stability of spectral measurement systems for fiber Bragg grating sensors

“…Applications involving FBGs are numerous, but many of them can be linked to the concept of SHM (Structural Health Monitoring). Let us mention as examples several industrial fields in which we were involved: mining & ground monitoring [1], underground storage [2], civil engineering [3], nuclear energy [4,5], high temperature environments [6], railway industry [7], composites materials, smart structures [8], biophotonics [9, 10]……”