Performance at collapse of adhesive bonding

When dealing with composite laminate bonded to pre-existing members (masonry, concrete, metal, wood), the performance at collapse of the adhesion is substantially given by two features: the failure load and optimal bonding length. The last one can be defined as the length required for ensuring the maximum value of the transferred load between the laminate and the substrate. Within the context of structural strengthening, many technical design formulae are available for predicting both the failure load and optimal bonding length, but they have been generally derived for special cases only. There is not a unique formula with a general validity regardless of the nature of the substrate (concrete, masonry, metal, wood). In this paper, a mechanical model previously formulated by the authors is used to derive closed form predictive equations for the failure load and optimal bonding length which have, instead, a general validity due to the circumstance that they account for the cohesive parameters of the interface as well as the mechanical properties of the composite laminate. Comparisons with results obtained by other authors are also given with reference to the composite–concrete interface.