Systematic mixed mode Ⅰ+Ⅱ fracture experiments on LC4CS Aluminium alloy compact-tension-shear (CTS)
specimens of 2?mm,4?mm,8?mm
and 14?mm thickness were designed and accomplished. Force-crack open displacement (Force-COD) curves and mixed crack initial angles with various thicknesses under all loading conditions were obtained. It is showed that the thickness and load mixity have a strong influence on specimen strength and crack initial angle. The strength of thin plate is higher than that of thick plate under pure Ⅰ mode; the strength of 4 mm-thick plate is the highest, 2 mm close to 8 mm, 14 mm the smallest under Ⅰ+Ⅱ mode; and the strength of all kinds of thickness is almost the same under pure Ⅱ mode. The crack
initiation direction in 2 mm-thick
specimens is mostly the same as that in 14 mm-thick specimens under all sorts of mode mixity. However, it is a little higher in 4 mm-thick specimens and much lower in 8 mm-thick specimens. The maximum tangential stress criterion established on the basis of plane hypothesis is adequate to predict the direction of crack initiation of 2 mm and 14 mm plates under mixed mode load condition, however not suitable to 8 mm-thick plates.