Strength of Aluminum Alloys Under Static Mixed-Mode I/II Loading Conditions

Abstract

Abstract Structures for aerospace and space applications often experience combination of tension and shear-loading conditions beside pure tensile opening loads (mode I). This paper presents the results of mixed-mode load tests conducted on two different grades of aluminum alloys frequently used in aerospace, automotive, and industrial structures. Testing was conducted using butterfly specimens and Arcan fixtures. Specimens were tested at different loading angles ranging from pure tension (mode I) to pure shear (mode II), as well as mixture of both modes I/II. Strength-loading-angle correlation was established. The results showed that the strength decreases linearly with increasing loading angle from pure tension to pure shear. About 45 %–47 % reduction in strength was observed upon changing loading scenario from pure tensile to pure shear. Displacements at different loading angles were measured using the digital image correlation (DIC) method and have been found to increase load mixity. Ratio of shear to tensile strength was calculated to be in range of 0.53–0.54 for aluminum alloys tested in this work. Crack extension and fracture mechanism deviated with the stress state. Finite-element modeling was also carried out and it was found to be in good agreement with the experimental results.