Abstract
Interfacial debonding in fiber-reinforced composites is a common problem, especially in external strengthening techniques. This investigation aims to determine the load during debonding, and discusses two practical design parameters for direct shear tests, which are commonly used to assess the mechanics of debonding. In this study, three different bond-slip cohesive laws and one finite fracture mechanics approach are considered to investigate debonding in direct shear tests by taking the effect of residual strength into account. For each model, load during debonding and its maximum value are given by closed-form expressions, which are then checked against experimental data reported in the literature. It is shown that using the interfacial mechanical properties extracted from one geometry, the debonding load of tests with different bond lengths and widths can be predicted without any fitting procedure. Moreover, effective bond length formulae are suggested for each model; one is the straightforward extension (accounting for residual strength) of a formula available in the Standards. The results illustrate the importance of considering residual strength in direct shear tests, even at debonding onset, with its effect being nonetheless higher for long bond lengths.
Highlights
One possible solution to increase or restore the load bearing capacity of an existing structure is to apply external reinforcements
Interfacial debonding in fiber-reinforced composites is a common problem, especially in external strengthening techniques. This investigation aims to determine the load during debonding, and discusses two practical design parameters for direct shear tests, which are commonly used to assess the mechanics of debonding
It is shown that using the interfacial mechanical properties extracted from one geometry, the debonding load of tests with different bond lengths and widths can be predicted without any fitting procedure
Summary
One possible solution to increase or restore the load bearing capacity of an existing structure is to apply external reinforcements. The debonding mechanism in the pull-push test for FRP-to-concrete joints was analyzed by Zhang et al [24] using a numerical approach called bonded-particle model. Biscaia et al [32] investigated the effect of residual bond strength on debonding behavior by applying an external pressure in double-shear tests. The mathematical modelling of the problem will be described, and closed-form expressions for the load values during the debonding process, for the maximum debonding load vs bond length, as well as for the effective bond length, will be presented according to three different interface cohesive laws and one finite fracture mechanics approach. They require proper modelling that goes beyond the scope of the present analysis
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