Experimental study on delamination migration in multidirectional laminates under mode II static and fatigue loading, with comparison to mode I

This paper presents an experimental investigation to better understand the mechanisms of delamination migration in multidirectional End Loaded Split (ELS) specimens. A stacking sequence susceptible to delamination migration was selected for this study and subjected to pure mode II static and fatigue loading. The static and fatigue results gave comparable migration mechanisms, however, differences were noted regarding the damage sequence, the fracture surface, the migration angle and the horizontal distances of migrated location to the front of pre-crack. Scanning Electron Microscopy (SEM) results indicated that fibre imprints and cusps were two dominant micro-features on the fracture surfaces for all specimens. Interactions between delamination and ply splits were observed and confirmed by X-ray CT scanning. Furthermore, comparison was made to understand the effects of loading modes (mode I and II) on delamination migration.