A Comparative Study of Bond Test Methods for Externally Bonded FRCM and SRG Composites

The bond behavior of externally-bonded fiber reinforced composites has been studied experimentally using different types of test methods. In this study the bond behavior of composite strips externally bonded to fired-clay brick masonry was tested using single-lap direct shear tests and hinged beam tests. The results obtained from the two test types were compared to investigate the effect of the test set-up on the load-carrying capacity of the matrix-fiber interface. Two different composite systems were considered: a fiber-reinforced cementitious matrix (FRCM) composite with a balanced bidirectional mesh of basalt fibers embedded in a hydraulic lime-based mortar, and a steel reinforced grout (SRG) with a sheet of ultra-high-strength unidirectional steel fiber cords embedded in the same mortar. The results are discussed and compared in terms of failure modes and applied load versus slip of the fibers response. An estimate of the matrix-fiber interfacial fracture energy of SRG-masonry joints is proposed using a global energy balance approach that does not require measurement of the strain in the fibers.