Analytical prediction model for fatigue crack propagation and delamination growth in Glare

This paper presents a new analytical model for constant-amplitude fatigue crack propagation of ‘through cracks’ (same crack length in all metal layers) in the fibre metal laminate Glare. The major concept is that the stress intensity at a crack tip in the aluminium layers of Glare is the factor determining the crack extension under cyclic loading. This means that the crack growth can be described with linear elastic fracture mechanics, including the contribution of the fibre layers and the with the crack growth associated delamination behaviour. The model describes the crack propagation of the fatigue cracks in the aluminium layers and the corresponding delamination growth at the aluminium/fibre interfaces perpendicular to the crack. The stress intensity factor at the crack tip is a function of the far field opening stress and the crack closing bridging stress in the aluminium layers. The bridging stress along the crack length is calculated on the basis of the crack opening relations for the individual mechanisms. It is then used to calculate the delamination extension, using a correlation between the delamination growth rate and the energy release rate.The prediction model is implemented in a numerical programme and is validated with a wide range of experimental data. A good correlation between predicted and experimental crack growth rates, crack opening contours and delamination shapes has been obtained.