A set of low velocity impact test are carried out on a composite wing box with areas of different thickness. Given the delamination threshold load (DTL) of an area, coefficients related to the energy release rate for mode Ⅱ shear fracture (G_Ⅱ) and the interlaminar shear strength (ILSS) are obtained, which are employed as references to predict the DTL of other areas of different thickness. The DTL prediction based on G_Ⅱ only performs well for the impacts caused by tups with the same diameter as that of the reference. The ILSS method is more accurate for the DTL prediction of impacts under different tup except the cases that the thickness of reference and target are differ greatly, while the method with contact radius correction improves the accuracy of prediction. The prediction by using linear fitting is also conducted and it shows that the accuracy are generally lower for the ILSS based mothed but higher for the Gn based method.
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