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Fracture mechanics of bonded FRP plate failure


Carbon Fibre Plates can be bonded to the tension faces of concrete structures to provide additional strength. Failure often takes place in the concrete layer just below the adhesive, either by peeling at the ends or by a crack propagating from an existing shear crack in the concrete. The conventional methods of analysis use finite elements to model the CFRP, the concrete and the adhesive. But the exact shape of the adhesive layer is unknown, and there is a singularity in the stress concentration at the interface. Furthermore, the condition of the interface is unknown, and unknowable - it is impossible to say if there are small voids in the adhesive and the exact surface texture cannot be known. Our analysis applies fracture mechanics principles - we assume that a crack is present and the method asks whether a propagation of the crack requires additional energy (in which case it will only propagate slowly as the load increases), or releases energy (in which case it will fail catastrophically).

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