Orientation-dispersed pseudo-ductile hybrid composite laminates - A new lay-up concept to avoid free-edge delamination

Multi-Directional hybrid composites can suffer from free-edge delamination, a damage mode that doesn't exist in Uni-Directional hybrid composites and can hinder the pseudo-ductility that can be achieved with thin-ply hybrids. This paper presents a new lay-up concept called 'orientation-dispersed' laminates to avoid this mode of damage in quasi-isotropic hybrids. It is shown that the energy release rates at the free-edges of orientation-dispersed layups are significantly lower than those in 'orientation-blocked' laminates. Finally, the experimental results from two quasi-isotropic layups with π/3 and π/4 intervals are presented showing a good pseudo-ductility with no free-edge delamination.