Experimental Study on Bonding Enhancement Methods between CFRP Strips and Steel Plates by Double-Lap Shear Test

One of the ways to confront the problem of debonding failure of externally-bonded carbon fiber reinforced polymers (CFRP), used for strengthening of steel members, is to provide a proper and practical bonding detail. If the high stress-concentration zones of the bonded strip such as curtailment points of CFRP or member discontinuities are suitably detailed or reinforced, then bonding resistance will be improved. This paper describes experimentally the methods which successfully prevent the premature debonding failure of externally-laminated steel members. The double-lap shear test set up has been chosen as a frame work to compare the results. Therefore bond zones includes shear stresses and peel stresses. The mechanical clamps in different arrangements were examined as a bondenhancement detail. Also, the effect of the length of the CFRP laminate was investigated along with different types of end mechanical anchorage. Finally, a simple and efficient bonding enhancement method has been proposed, in the form of overlapping the critical debonding zones using steel plates. The test results show that both the overlapping and clamping methods considerably increase the bonding resistance, but the former method is preferable because of its simplicity for installation and because in this case further increase of strength is obtained.