Tensile Tests of FRCM Coupons: The Influence of the Fiber-Matrix Bond Properties

Fiber-reinforced cementitious matrix (FRCM) composites are usually mechanically characterized by means of tensile and bond tests. The load responses provided by tensile tests of FRCM coupons are typically constituted of three phases, namely the uncracked, cracking, and fully cracked phase. Tensile tests can be performed by either transferring the force to the matrix (clevis- or clamping-grip test) or to the bare fibers (direct gripping of the fibers). The bond behavior of FRCM composites is generally investigated using single-lap shear test setups, which allow for the evaluation of the stress-transfer mechanism within the matrix, at the matrix-substrate interface, and at the matrix-fiber interface. Within the framework of fracture mechanics, results of single lap shear tests allow a cohesive material law (CML) to be calibrated for the weaker interface that is activated during the test. In this paper, a polyparaphenylene benzo-bisoxazole (PBO) fiber-matrix CML calibrated by the authors in previous works is introduced in an analytical model of FRCM tensile tests in order to verify if it allows the cracking process to be accurately predicted. The model allows for the introduction of different boundary conditions reproducing the different tensile test setups listed above. In particular, the boundary conditions associated with the gripping of the bare fibers are employed in this work and the results of the model are compared with experimental results of tensile tests of the same FRCM composite employed to calibrate the CML.