Finite Element Modeling of Mode I Failure of the Single Contoured Cantilever CFRP-Reinforced Concrete Beam

The single contour cantilever beam (SCCB) test method has been developed with the intent to capture Mode I opening failures of CFRP-reinforced concrete beams. Recent development in the method explores possible shifting damage into the concrete substrate by using the International Concrete Repair Institute (ICRI) Surface Profile Level Three (SP3) as the desired CFRP bonded interface to concrete. To validate and explain the interface fracture behavior, finite element analysis using special cohesive elements has been performed. The cohesive element allows separation of the concrete substrate from the CFRP. This paper presents the simulation of laboratory test results, where failure in the substrates has been successfully reproduced. The simulation results indicate that finite element method using cohesive elements can successfully replicate Mode I critical strain energy release rate and the peak capacity of the laboratory tests and may have the potential to simulate actual applications. 1. Introduction Several laboratory methodologies have been developed over the past few years to measure Mode I critical strain energy release rate involving composite wrapped concrete beams. Failures of representative methodologies designed to isolate Mode I opening failure of a fracture interface include the modified double cantilever beam (DCB) method [1], the peel test method [2], the membrane peeling method [3], and the single contour cantilever beam (SCCB) method [4]. All the above methods are variations of each other with different strengths and weaknesses, depending on the application. However, the SCCB method exclusively ensures that the failure will always be the first mode. A second advantage of the SCCB method is the elimination of compliance measurements. The SCCB method was first developed by Boyajian [5] and has been utilized to determine the critical strain energy release rates at the bonding interface between concrete and carbon fiber-reinforced polymer (CFRP) [4, 6, 7]. Figure 1 shows the schematics of the SCCB test including the test specimen that consists of concrete base plate, CFRP bonded layer, the wood contour, and the experimental setup that includes a steel strap for pulling on the wood contour. Figure 2(a) shows the actual test setup within a MTS test apparatus with arrow indicating the direction of pull load. With the SCCB test, the high tensile capacity LVL is loaded with a normal force, P, inducing Mode I failure behavior of the CFRP to concrete interface and thus avoiding the arm break-off failure. The starter crack is created by debonding the