Evaluation of the mechanical tensile behaviour of FRCM and NFRCM composites - analysis of a non-linear constitutive relation

The present dissertation intended to contribute to research and knowledge on the tensile behaviour of composite materials; in particular, samples were made with lime-based mortar matrix and reinforced with natural or carbon fibers impregnated with an adhesion promoter. Composites reinforced with natural fibers have the potential to be applied in the rehabilitation and strengthening of structures in developing countries, using eco-friendly materials, available resources and at a low-cost solution. Of these samples, the influence of different parameters on the tensile behaviour has been studied, such as: the number of composite layers from 1 to 3, the thickness of the layer and the geometry of the fabric. After the curing period, the mechanical behaviour was analysed through tensile tests, whose results are graphically displayed. The composites reinforced with natural fibers showed clearly three distinct behavioural phases: a stage in which the material is uncracked, a crack development phase and a stage of expansion of the existing cracks. In composites reinforced with impregnated carbon, the crack development phase is less marked due to the presence of the impregnating agent. For composites reinforced with carbon fiber and adhesion promoter, a non-linear constitutive equation was also analysed. A good approximation of the bilinear curve of the material has been obtained, showing that it can be a good tool to predict the mechanical behaviour for a future design.