Bond-free CFRP as a new concept for strengthening steel

According to a new study, buckling performance and compression capacity of structural steel elements can be enhanced using bond-free carbon fiber reinforced plastic (CFRP) laminates.

CFRP offers a range of advantages such as its light weight and high strength, as well as its fatigue and corrosion resistances. Therefore, it is preferable for strengthening steel members. Until today, CFRP is mainly being attached to steel surfaces using adhesive. This bonding technique apart from the fact that it requires very careful steel surface treatment before the CFRP installation, it is vulnerable to environmental exposure during service life of CFRP, something that can cause significant decrease in strengthening.

The research conducted by the Structural Engineering Laboratory of the Department of Architecture and Civil Engineering at Toyohashi University of Technology showed that, alternatively, if CFRP is not bonded onto the surface of the steel element, it can offer structural strength due to its flexural rigidity.

The experiments showed that the unbonded CFRP strengthening method leads to a delay of the buckling phenomenon, as well as to an increase of the compression capacity of steel bars. The results of this study make the research team believe that the bond-free CFRP method can be applied also in fields such as aerospace engineering, and in the automotive and marine industries. The study was recently published in Construction and Building Material journal.