Mixed-mode fracture toughness versus thickness and yield strength in aluminum alloys

Variations in in-plane mixed-mode fracture toughness versus changes in thickness of shear CT (CTS) specimens and loading direction and effects of yield strength of different aluminum alloys have been investigated by experimental testing and numerical analysis. Several samples were made by Al2024-O, Al6061-T6 and Al7075-T6 alloys. Based on the results, increasing the thickness reduces the mixed-mode fracture toughness and near to the critical thickness, this reduction is lesser. Increase in mixed-mode loading angle for brittle materials has not significant effects on the toughness while in softer materials by changing the angle from 15 degrees to 60 degrees, the amount is halved. Near the mode I fracture conditions, there is no meaningful relationship between the yield strength and fracture toughness but with an increase in the second mode effects, these parameters will be proportional. The mixed-mode toughness of the alloys with different thicknesses can be calculated numerically with a precise accuracy by applying failure load in the analysis.