Testing vs Application Issue for Fiber Reinforced Materials

The strengthening of masonry structures is nowadays performed by means of High-strength fibers embedded in inorganic matrix (Fiber Reinforced Cementitious Mortar materials, FRCM). In such materials lime or cement-based matrix is used instead of epoxy adhesive to reduce debonding issues between substrate and matrix, however some sliding phenomena and cohesive failures between fibers and the matrix mortar can occur. The main aim of this research is to examine the impact on the FRCM efficiency of the mechanical properties of fiber and matrix and potential geometrical defects, which are possible in real field applications. Discussion is based on the predictions obtained through an analytical model recently developed by the authors to investigate the local effects of adherence that affect the mechanical behaviour of FRCMs. The topic is particularly important and greatly discussed in the scientific community and among manufactures and practitioners, because the bond test has a significant role, as it is used for the qualification of the material, providing sometimes very scattered results. The model represents an attempt to reproduce the variability typically found in the experimental bond tests performed on FRCM systems for qualification purposes and to find solution to reduce this scatter and, overall, correlate this scatter to the performance in real application. The model was then applied to the typical cases of PBO-FRCM and Glass-FRCM to analyse slip and stresses in the bundle and in the matrix for different defects due to application issues.