Enhancing buckling capacity of angle steel using unbonded CFRP laminates processed by Vacuum-assisted Resin Transfer Molding (VaRTM)

Abstract

The carbon fiber reinforced polymer (CFRP) adhesive-bonding technique has been increasingly developed for strengthening steel structures. However, the application of this strengthening method is still considered ineffective since it requires complicated and burdensome steel surface treatments. The bonding strength of CFRP on steel, on which this method highly depends, is also prone to performance decreases due to inevitable environmental exposures. Alternatively, unbonded CFRP strengthening is proposed in this study. A total of twelve specimens are prepared and tested to evaluate the possibility of application of this strengthening method in enhancing buckling performance of angle steels. All CFRPs on the strengthened specimens are created through a process of Vacuum-assisted Resin Transfer Molding (VaRTM). It is concluded from the investigation results that the unbonded CFRP is effective in strengthening angle steels, where the buckling strength enhancements by 8.5%-54.3%. The strength increase is clearly affected by CFRP length, number of CFRP layers, and steel’s slenderness ratio. A change in the curvature of the specimens due to the presence of unbonded CFRPs can also be observed. The VaRTM process produces higher fiber content of laminates. Analytical studies carried out at the end of this paper provide a reasonable solution for strength design and a good correspond for post-buckling prediction.