An experimental and numerical study has been carried out to understand and predict the compressive failure performance of quasi-isotropic carbon-epoxy laminates with out-of-plane wrinkle defects. Test coupons with artificially induced fibre-wrinkling of varied severity were manufactured and tested. The wrinkles were seen to significantly reduce the pristine compressive strength of the laminates. High-speed video of the gauge section was taken during the test, which showed extensive damage localisation in the wrinkle region. 3D finite element (FE) simulations were carried out in Abaqus/Explicit with continuum damage and cohesive zone models incorporated to predict failure. The FE analyses captured the locations of damage and failure stress levels very well for a range of different wrinkle configurations. At lower wrinkle severities, the analyses predicted a failure mode of compressive fibrefailure, which changed to delamination at higher wrinkle angles. This was confirmed by the tests.

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This work presents a cohesive interface model for predicting interlaminar failure of composite laminates under tension-tension fatigue loading. The model features improvements on previous formulations and utilizes four-integration-point elements, which offer several new advantages, while maintaining the merits of the previous single-integration-point elements. An element-based crack tip tracking algorithm is incorporated to confine fatigue damage to crack-tip elements only. A new local rate approach is proposed to ensure accurate integration of strain energy release rate from local elements. Furthermore, a dynamic fatigue characteristic length is proposed to offer a more accurate estimation of fatigue characteristic length in complex threedimensional cases. Fatigue initiation is incorporated by using a strength reduction method, without changing the propagation characteristics. The numerical approach has been verified and validated using multiple cases and was then applied to fatigue damage development in open-hole laminates, where a good agreement between numerical analysis and experimental results was obtained.

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.