Comparison between bolt clamping force and composite patches for repairing aircraft structures of aluminum alloy 2024-T3

Many parts used in various industries are subjected to multiaxial stresses during service phase, and since cracks can be a source of failure in the parts, it is extremely important to analyze the strength of cracked structures under multiaxial loads, and improve the structures fracture strength. In the present research, the effect of clamping force resulted from bolted pre-tension and composite patches on enhancing fracture strength of edge cracked rectangular samples made of aluminum-alloy 2024-T3 are evaluated both experimentally and theoretically. The cracked laboratory samples were tested using a modified version of Arcan fixture to develop pure tensile, pure shear, and mixed modes of loading. Further, finite-element simulations were utilized to find stress intensity factors to explain the experimental test results. The experimental results indicate a significant increase in the tensile strength of repaired parts by the bolt clamping and composite patches compared to simple cracked samples. Repaired samples with composite patch and bolt clamping exhibited up to 44% and 24% increase in tensile strength under pure tensile mode, respectively. However, in pure shear mode, the fracture strength increased to 18% and 9% by bolt clamping and composite patch, respectively.