Debonding of composites on a curved masonry substrate: Experimental results and analytical formulation

Externally bonded mortar based composites have become a popular technique for strengthening masonry arches and vaults. The effect of the curved substrate on the bond properties is one of the key factors affecting their structural behaviour. This paper presents the results of an experimental campaign of debonding tests on straight and curved substrates made of bricks assembled with mortar and strengthened either with Carbon Fibre Reinforced Cementitious Matrix (CFRCM) or Steel Reinforced Grout (SRG). The experimental results get insight into the failure mechanisms that take place in mortar based composites and disclose the effect of the substrate curvature on the interfacial strain distribution and on the load–displacement response. The experimental results are compared with the outcomes of a predictive model, proposed in this work, which provides a closed-form analytical solution to the debonding process of a thin plate on a rigid substrate with constant curvature. The model, which is based on an interface cohesive law, coupled in the tangential and normal directions, as a consequence of the curvature, is able to predict the decrease in bond stiffness and strength for increasing curvature, as shown by experimental results.