Abstract

Aluminum alloys are primary structural materials in aircraft fuel systems, where jet fuel can significantly affect the crack propagation behavior of the materials. This paper presents a model for calculating the crack growth rate of aluminum alloys in jet fuel environment. The model is based on elastoplastic fracture mechanics and revises the interaction terms in the linear superposition model by taking into account corrosion damage and crack closure effects. The derivation process of the model is discussed in detail. To validate the efficacy of the model, fatigue crack propagation tests were conducted on three types of aviation aluminum alloys, namely 2524-T3, 7050-T7451, and 7075-T62, in the jet fuel environment. The experimental results were compared with crack growth rates in the laboratory air environment. Findings indicate that the proposed model effectively captures the primary trends observed in the experimental data. In addition, the failure surfaces of the specimens were observed using a super-depth-of-field optical microscopy system. When subjected to jet fuel, among three materials tested, the 7075-T62 alloy was found to have the roughest failure surface. This increased roughness contributing to crack closure was identified as one of the reasons why its fatigue crack growth rate is significantly lower in the jet fuel than in air.