Tensile Testing of FRCM Coupons for Material Characterization: Discussion of Critical Aspects

Tensile tests on fabric-reinforced cementitious matrix (FRCM) coupons are used to evaluate the tensile mechanical properties of the composite. Bond tests, typically single-lap shear tests, are used to characterize the interfacial properties between the FRCM composite and the substrate and to identify the interface at which debonding takes place. Some FRCM composites exhibit debonding at the fiber-matrix interface, which is characterized by a cohesive material law (CML) that can be obtained from bond tests. The authors have shown that for these composites, the CML can be fed into an analytical model to predict the results of tensile tests. In this paper, the same model is used to highlight some critical aspects of the clevis-grip tensile test. In particular, it will be shown that the length of the gripping devices, the length of the specimen, and the gauge length adopted to measure the deformation of the specimen have a strong influence on the results of the tensile tests. In addition, an analogy between the clevis-grip tensile test and single-lap shear test will point out that the tensile test is a bond test and can be used to determine the bond capacity rather than the tensile properties, which will be proven to be non-uniquely defined by this test.