High performance quasi-isotropic thin-ply carbon/glass hybrid composites with pseudo-ductile behaviour in all fibre orientations

This study exploits the potential of thin-ply carbon/glass hybrid laminates to generate high performance Quasi-Isotropic (QI) composite plates that show pseudo-ductility in all fibre orientations under tensile loading, overcoming the inherent brittleness of conventional composites. Two types of QI lay-ups with 45° and 60° intervals, i.e. [45/90/-45/0] and [60/-60/0], were used to fabricate novel architectures of a QI T300-carbon laminate sandwiched between the two halves of a QI S-glass laminate. The fabricated plates were then loaded in all their fibre orientations. The laminates were designed by choosing an appropriate ratio of the carbon thickness to the laminate thickness using a robust analytical damage mode map. The experimental results verified the analytical predictions and showed a desirable pseudo-ductile failure in all the fibre orientations. Microscope images taken through the laminates thickness showed fragmentations (fibre fractures in the carbon layer) appearing only in the 0° carbon plies. A hybrid effect was observed, with an increase in strain and stress to failure of the carbon fibres, which was found to be dependent on the stiffness of the plies separating the 0° carbon plies and the plies adjacent to the 0° carbon plies. Altering the stacking sequence changes the stiffness of the separator and adjacent plies, therefore, leads to changes in the pseudo-ductile characteristics such as the initiation and final failure strains.