Investigation of the effect of composite patch repair on the life of a plate with two lateral cracks

Abstract

This paper presents a study on the effect of composite patch repair on the fatigue life of an aluminum alloy plate containing two lateral cracks and subjected to cyclic tensile stresses applied to its upper and lower parts. The investigation considers several parameters, including the load ratio between minimum and maximum stresses (0, 0.3, 0.6, and 0.7), the cracking speed as a function of the stress intensity factor (Delta K), and the influence of the plate material. Among the alloys examined were 2024-T3, 2024-T351, and 7075-T73. The study identifies the material most resistant to cyclic loading. The plate is analyzed in both unrepaired and repaired conditions, with repairs performed using two different composite patches: boron/epoxy and graphite/epoxy. The results demonstrate that patch reinforcement significantly improves fatigue resistance, with boron/epoxy patches providing the greatest enhancement. The study concluded that the AL 2024-T3 material presents better results compared to the other two materials. These findings confirm the effectiveness of composite patching as a promising technique for extending the service life of cracked structures.