Analytical modelling of the tensile response of pbo-frcm composites

Fiber-reinforced cementitious matrix (FRCM) composites are usually mechanically characterized by means of tensile and bond tests. The load responses provided by tensile tests are typically comprised of three phases, namely the uncracked, cracking, and fully cracked phase. The uncracked phase ends when the applied stress attains the matrix tensile strength. During the cracking phase, multiple cracks form in the matrix and the behavior of the specimens is governed by the shear stress acting at the fiber-matrix interface. During the fully cracked phase the width of the cracks increases and the applied load is carried by the textile in the cracked cross-sections. The bond behavior of FRCM composites is generally investigated using single-lap direct-shear test set-ups, which allow for the evaluation of the stress-transfer mechanism within the matrix, at the matrix-substrate interface, and at the matrix-fiber interface. Results of single-lap shear tests have been employed to calibrate a cohesive material law (CML) that describes the bond behavior between the poliparafenilenbenzobisoxazole (PBO) fibers and the embedding matrix of a PBO-FRCM composite. In this paper, the PBO fiber-matrix CML obtained from direct-shear tests is employed in an analytical model that describes clevis-grip tensile tests of a PBO-FRCM composite in order to verify if the cracking process can be accurately predicted by the analytical model.