Analytical hybrid effect prediction and evolution of the tensile response of unidirectional hybrid fibre-reinforced polymers composites for civil engineering applications

The performance of a progressive damage model in quantitative hybrid effect prediction of a comprehensive set of different 16 unidirectional interlayer (layer-by-layer) hybrid composites was assessed. Composites, produced by the hand lay-up method, made out of four different commercially available dry unidirectional fabric materials, namely high-modulus carbon, standard carbon, E-glass and basalt, were tested. Tensile tests on single fibres were performed in order to determine their Weibull strength distribution parameters, which were used as inputs of the progressive damage model. Reasonably good agreement between analytical and experimental hybrid effect results was obtained, which allowed to estimate satisfactorily the reference strengths of the unidirectional low strain composite materials. Next, an existing analytical model for the simulation of stress–strain curve of hybrid composites was adapted to contemplate the hybrid effect, which allowed to predict the following properties of unidirectional hybrid combinations: ‘yield’ stress (or pseudo-yield stress), pseudo-ductile strain and strength. It was verified as well that predictions of the three properties referred to were in close agreement with the test results. Finally, damage mode maps were used in the analysis of these properties and, furthermore, of the hybrid effect and the elastic modulus of hybrid combinations.