Researchers at the Toyohashi University of Technology laboratory have developed a new concept that can use non-bonded carbon fiber reinforced plastic (CFRP) laminates to strengthen steel in critical building structures, thereby improving Buckling performance. This method does not require steel surface treatment before CFRP treatment, because CFRP is not bonded to the surface, and its flexural rigidity helps improve structural strength.
Following the success of concrete reinforcement in the field of civil engineering, CFRP has now developed into a method of strengthening steel members instead of using traditional steel plates. CFRP is the technology of choice because of its many advantages, such as light weight, high strength / weight ratio, and excellent fatigue resistance and corrosion resistance. However, to date, research and development using CFRP to strengthen steel have focused on bonding technology, which involves the use of adhesives to attach CFRP to the steel surface. Bond reinforcement has the disadvantages of complex surface and time-consuming, and needs to be processed before installing CFRP. In addition, since it is exposed to the environment throughout its service life, the bond strength performance between steel and CFRP (as a key aspect of this strengthening technology) is also significantly reduced. Replacing this method with other bonding CFRP techniques is not a particularly suitable solution because it is unlikely to be cost-effective.
The research team developed a method of using CFRP to strengthen steel, for which they did not bond it to the steel surface. Facts show that this method can delay buckling and increase the compressive capacity of the steel bar, where the capacity gain is affected by the number of carbon fiber layers used.
The lead author explained: “As an alternative to the steel reinforcement method using CFRP bonded to the steel surface, we developed this CFRP method without bonding. The main advantage of this method is that it is easier and more time-saving to implement, Especially when applying it to existing elements of building structures. There is no longer any need for troublesome steel surface treatment, such as sandblasting or manual sanding, which can save a lot of costs. "
The team leader added: “Almost all previous studies used glued joints to strengthen CFRP steel components. This method is quite complicated because it requires proper steel surface treatment before applying CFRP to CRP. In CFRP and steel Acceptable bonding between surfaces is achieved. Surface treatment conditions can also affect bond strength. "
"In addition, we cannot perfectly estimate the effect of exposure to the environment on the bonding performance between CFRP and steel during the service life. Therefore, we tried to improve the traditional method by developing our own non-bonding strengthening method."
He said: "Unbonded reinforcement methods are effective, easy to apply and easy to manage." He added: "However, our method cannot transfer stress smoothly, so it is necessary to establish an appropriate mechanical model. Therefore, we conducted Mechanical simulations and experiments to prove this. "
The findings of their work convinced members of the research team that the unbonded CFRP method can be applied not only in civil engineering, but also in other fields, such as the aerospace, automotive, and marine industries. It is expected to adopt this promising new method to quickly produce innovative high-quality products.