This research involves strengthening existing civil infrastructure using fiber reinforced polymer (FRP) composites. FRP composites are currently applied to bridges, buildings or other reinforced concrete structures in order to provide additional load carrying capacity. The application procedure for FRP strengthening systems is very similar to applying wallpaper: dry fibers (typically carbon) are saturated on-site and applied to the surface of the concrete to the FRP composite via shear stress across the bond line. Serious problems can arise if these systems are not installed properly and air bubbles are present between the FRP and the concrete.
One method for determining whether or not an FRP system is properly bonded to concrete involves thermal imaging. The general concept behind the technique is to apply heat to the surface of an FRP composite using standard IR heat lamps. This will result in a thermal front that travels from the surface into the concrete substrate. If any defects or air voids are present at the FRP/concrete interface, the heat flow will be interrupted and a "hot-spot" will occur on the surface. This hot-spot can be detected using an infrared camera.
Specific objectives for this summer position are aimed at applying the infrared thermography technique to investigate the criticality of defects in FRP systems applied to reinforced concrete. Several small-scale reinforced concrete beams will be constructed and FRP composites will be used to strengthen these beams in flexure. Defects will be implanted at the FRP/concrete interface and the beams will be subjected to fatigue loading. Infrared thermography inspections will be conducted at various stages in the fatigue loading process. The purpose of these inspections will be to determine if the implanted defects adversely affect the fatigue life of the FRP system.
The student will be responsible for the design and construction of the small-scale beams, applications of the FRP systems, and subsequent fatigue loading experiments. The student will also gain experience using a state of the art thermal imaging system. Various data analysis techniques for processing thermal imaging data will also be investigated.