Experimental study and numerical simulation for bond behavior of interface between CFRP and steel

The bond performance between carbon fiber reinforced polymer composites (CFRP) and steel plate is one of the key problems in strengthening steel structure with CFRP. Tensile-shear tests of 17 CFRP lamina-steel plate single-lap specimens were conducted, the mechanical behavior and failure modes of CFRP-steel interface of specimens with different epoxy adhesives and CFRP materials were studied. The influences of adhesive types and CFRP materials on interfacial bond-slip constitutive and shear bearing capacity were analyzed, and the calculation methods of interfacial shear capacity were discussed. Results show that interface failure modes and ultimate bearing capacity are significantly different for specimens with different adhesives or CFRP materials. The failure mode for specimens with Sika 330 and Lica adhesive is the mixed mode of CFRP-adhesive and steel-adhesive interface debonding, and failure modes for specimens with Araldite adhesive, Sika 30 adhesive, and SF (Sika S512/80) lamina are CFRP superficial delamination, adhesive failure, and CFRP deep layer delamination, respectively. The ultimate bearing capacity of Araldite specimen is 1.7~2.9 times of the other specimens. No descending branches are found in bond-slip curves for Sika 330, Araldite, and Lica specimens, which are characterized by brittle fracture of interfaces. However, low descending branches are found in bond-slip curves for Sika 30 and SF specimens, and forewarning signs occur before interfacial failure. The bond-slip constitutive model for the SF specimens can be simplified to trilinear model, while those for the other specimens can be simplified to bilinear models. The ultimate bearing capacity for SF specimens should be represented by Xia-a model, while those for the other specimens can be represented by Xia-b model. The mechanical behavior of the interface is numerically simulated based on cohesive zone model. Results show that the nonlinear mechanical behavior of the interface can be well simulated by the cohesive zone model, the influence of peeling stress on the bond strength of interface is small for these single-lap specimens.