First flexural and interlaminar shear failure in symmetric cross-ply carbon-fibre laminates with different response under tension and compression

A significant characteristic of composite materials is the difference in behaviour under tensile and compressive loads in their principal directions. The influence of this feature on the results of three point bending tests is reviewed. Symmetric cross-ply laminates comprised by unidirectional and continuous carbon fibre-reinforced epoxy laminae are analysed. The technique of the homogenised section is used for deriving an analytical model which predicts the first failure mode produced and its location. Three different cross-ply laminates, [902 02]2, [02 902]S and [03 902]S, are constructed and tested in order to assess experimentally the rightness of the exposed theory. Microscopy analysis is developed for determing whether flexural or inter-laminar shear failure modes are obtained experimentally. The analytical estimations are in good agreement with the experimental observations and measurements.