Process and Health Monitoring of FRP by Rayleigh-scattering Based Distribution Optical Fiber Sensors

摘要

Distribution optical fiber sensors are attractive because of capability of distributionsensing of strain for large-scale FRP structures. Recently, Rayleigh-scattering baseddistribution optical fiber sensors, which has high spatial and strain resolution, havebeen developed. Therefore, it is expected that local strain distribution produced bysuch as local damages or unevenness of temperature distribution can be monitored bythe Rayleigh-scattering based sensors.In the present study, feasibility studies of process and health monitoring of FRP bythe Rayleigh-scattering based sensors were conducted. In the monitoring of VaRTMprocess of textile GFRP, flow front of resin impregnation and process-induced strainwere monitored. From the monitoring results of impregnation process, it was foundthat the flow-front of the resin could be observed as the maximum compressive strainin the strain distribution. From the strain curves after start of heating process (40minutes), the optical fiber sensor could measure thermal strain by heating from 40 to100 minutes, curing shrinkage from 100 to 150 minutes and thermal shrinkage bycooling from 150 to 170 minutes successfully. Therefore, it can be concluded that theRayleigh-scattering based sensors could monitor impregnation status of resin anddistribution of process-induced strain during VaRTM process.In the health monitoring, damage identification of cross-ply GFRP laminates withdelamination by the attached distribution optical fiber sensors was carried out. Threetypes of specimens, no delamination, delamination between the central layers anddelamination between the outer layers were prepared. The distribution sensor wasattached on the bottom surface. From the results, it appeared that the strain variedlargely on the delaminated section and the measured distribution is similar to theanalyzed one. Therefore, it was found that the Rayleigh-scattering based sensors couldidentify delamination from surface strain distribution.