Flexural Damage Response Of Symmetric Cross-Ply Carbon Fiber Reinforced Laminates: Effects Of Thickness And Ply-Scaling Technique

Advanced fiber reinforced composite materials have become relevant in aerospace, automotive, wind energy, marine, and civil engineering applications due to their high specific stiffness and strength, corrosion resistance, and fatigue performance. In addition, composite materials are subjected to complicated loading conditions, such as bending, tension, compression, and twisting. However, a significant characteristic of composite materials is their unequal compressive/tensile response. The aim of this work is to highlight the effects of laminate thickness and the type of scaling technique on the flexural response of symmetric cross-ply CFRP laminates, taking into account the unequal compressive/tensile response of these laminates. This different response has been analyzed in order to determine the failure mode exhibited by the laminates under flexural loading (flexural or interlaminar shear failure) and, additionally, where it was produced for design purposes. Three-point bending tests were carried out to determine the mechanical response in terms of strength and stiffness of the different CFRP laminates. Optical micrographs of fracture surfaces were used to assess failure mechanisms of the different configurations. It was observed that the effect of laminate thickness was significant. Thicker laminates show lower strength and strain to failure, but, conversely, higher bending stiffness. In addition, the results depict a significant change on the flexural damage performance with the stacking sequence and the type of scaling technique (sublaminate/ply-level) due to unequal compressive/tensile response. Finally, the results obtained demonstrate that introducing ply clustering had a negative effect on the [90/0] configuration, but, conversely, an improvement of the flexural damage performance on the [0/90] configuration.