Finite element analyses of mode I interlaminar delamination in z-fibre reinforced composite laminates

This paper presents a detailed numerical study of the mode I interlaminar fracture of carbon/epoxy composite laminates with z-fibre reinforcement. The study was performed using a double cantilever beam configuration. A finite element model was developed using thick-layered shell elements to model the composite laminates and non-linear interface elements to simulate the through thickness reinforcements. An existing micro-mechanical solution was employed to model the material behaviour of the interface element. The numerical analysis showed that z-fibre pinning were effective in bridging delamination when damage had propagated into the z-fibre field; these pins provided crack closure forces that shielded the delamination crack from the full delaminating force and moment due to applied loads. Therefore, the z-fibre technique significantly improves the crack growth resistance and hence arrests or delays delamination extension. The numerical results were validated against experimental data. With reference to structural integrity this technique can be used to design a more damage tolerant structure.