A progressive damage analysis including delamination for fiber reinforced composites

A finite element model for progressive in-plane damage and interfacial delamination was presented for cross-ply composite laminates. The commercial finite element software ABAQUS/STANDARD was used for the thesis research. Each composite laminae was modeled as layers of shell elements based on Mindlin's plate theory, thereby achieving computational efficiency. Displacement continuity was established across the layers of shell elements. Interlaminar stresses were recovered at the interface with the use of multi-point constraints or an interface layer. Several material constitutive relations were developed to simulate the in-plane damage, such as fiber breakage, matrix cracking and in-plane shear failure. Interlaminar delamination was simulated by removing the displacement constraints or by reducing the stiffness of the interface layer. The delamination scheme was validated for a composite beam subjected to sinusoidal loading by an elasticity solution extended from the Pagano's problem. The finite element analysis results matched well with the elasticity solution for different interface bonding conditions. Composite laminates with different stacking sequences were subjected to impact loading. The results from the finite element analysis compared well with the experimental results qualitatively. The typical penny-shaped delamination area was observed at the interface and matrix cracking was observed along the fiber direction. However, the delamination size was about 50% lower than the experimental results.