Energetic balance in the debonding of a reinforcing stringer: Effect of the substrate elasticity

An effective way to strengthen deteriorated concrete or masonry structures is to glue to them, at critical regions, strips or plates made of Fiber Reinforced Polymers (FRP). The reliability of this technique depends upon interfacial adhesion, whose performance is usually evaluated through an energetic balance, assuming that the support is rigid. The present study analyzes the contact problem between reinforcement and substrate, both assumed to be linear elastic. The solution of the resulting integral equations is expressed in terms of Chebyshev polynomials. A generalization to this problem of the Crack Closure Integral Method developed by Irwin allows to calculate the energy release rate associated with the debonding of the stiffener. Energetic balance à la Griffith emphasizes the role played by the length of the stiffener and the deformation of the substrate, predicting load vs. displacement curves that, in agreement with experimental measurements, exhibit a snap-back phase.