This research is aimed to develop repair and reinforcement methods with excellent workability and usefulness for steel structural members that have been damaged through aging. Fiber-reinforced plastic, which has been used in various fields in recent years, is also used for building and civil engineering. Especially, it is assumed that carbon fiber-reinforced plastic (CFRP) has light weight and high-strength mechanical properties. Conventional methods of repair and reinforcement using CFRP are mainly hand-lay-up molding methods using carbon fiber sheet and adhesion methods using CFRP plate. However, both methods have some issues. Therefore, we apply the vacuum-assisted resin transfer molding to repair and reinforce steel structural members; the proposal of a construction procedure and a basic investigation of bond strength were carried out. In the basic investigation, a double-strap tensile shear test and a three-point bending test of steel/CFRP composite specimens were carried out. In the double-strap tensile shear test, in order to improve the adhesiveness of CFRP, the adhesive strength against shear force was compared between the specimen pre-coated with resin and a specimen not coated with resin after surface treatment. The results showed that the pre-coated specimen had high strength and stability. In the three-point bending test, bond strength and fracture mode against bending force were analyzed using adhesion length and number of laminated carbon fiber sheets as parameters. From the finite element method, the stress when peeling occurs due to the bending deformation was estimated and compared with the experimental result.
Slope-assisted Brillouin optical correlation-domain reflectometry (SA-BOCDR) is a recently developed structural health monitoring technique for measurements of strain, temperature, and loss distributions along optical fibers. Although the basic operational principle of this method has been clarified, no measurements using optical fibers embedded in actual structures have been reported. As a first step towards such practical applications, in this study, we present an example of an SA-BOCDR-based diagnosis using a composite structure with carbon fiber-reinforced plastics. The system’s output agrees well with the actual strain distributions. We were also able to detect the breakage of the embedded fiber, thus demonstrating the promise of SA-BOCDR for practical applications.
The ultrasonic welding of polymer optical fibres (POFs) onto carbonfibre-reinforced polymers for advanced fibre-optic sensing is demonstrated. The relationships among the welding time, preload, optical loss, and adhesive force are fully evaluated. A high-speed camera to monitor changes in the cross section of the POF during the ultrasonic welding is also used.
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