Characterization of delamination growth behaviour of hybrid bonded laminates

The objective of this work is to study the delamination growth behaviour of hybrid composite-aluminium bonded laminates. A modified Double Crack Lap Shear (DCLS) specimen was chosen for this study. An expression relating the delamination size and the compliance of a DCLS specimen was derived, and a test method for the delamination growth rate in DCLS specimens developed. The delamination sizes and the delamination growth rates of DCLS specimens were determined by monitoring the compliances of specimens during fatigue. Delamination growth rates at different stress ratios (R = 0.1, 0.3, 0.5) were measured. A Walker-type equation for the delamination growth rate was obtained by a multiple linear regression analysis. It was shown that the compliance method for determining the delamination growth rate of DCLS specimens is not only convenient and practical, but also accurate. The delamination size in DCLS specimens increases linearly with cycles during fatigue, i.e. delamination growth rate is constant, independent of delamination size. The energy release rate was adopted to characterize delamination growth behaviour. Good agreement between the Walker equation and test results of the delamination growth rate was found.