Issue 71

M. Abdulla et alii, Fracture and Structural Integrity, 71 (2025) 124-150; DOI: 10.3221/IGF-ESIS.71.10

intermediate, suggesting moderate resistance to crack propagation. The graphite fibres provide a good balance of stiffness and strength, which contributes to better performance compared to glass/epoxy but not as effectively as boron/epoxy. Glass/epoxy composites, with Young's modulus of 50 GPa, exhibited the highest SIF values due to their lower mechanical properties. The reduced tensile strength and stiffness of glass/epoxy result in higher stress concentrations at crack tips under mechanical loading, leading to elevated SIF values and lower resistance to crack propagation. The inherent material limitations of glass/epoxy composites mean that they are less effective in distributing the applied stresses, thus increasing the likelihood of crack growth under mechanical loading. Overall, the findings highlight the superior performance of boron/epoxy in reducing SIF under mechanical loading and enhancing the structural integrity of repaired plates, making it the most effective material among those studied.

Figure 10: SIF for different patch sizes under mechanical loading.

Figure 11: SIF for different patch materials under mechanical loading.

Adhesive materials A boron/epoxy composite patch was applied to a plate with a crack length of 10 mm to evaluate three different adhesive materials: Araldite 2015, AV138, and FM73. The tests were conducted under mechanical loading conditions. The result, as shown in Fig. 12, demonstrated that FM73 exhibited the highest SIF value among the adhesives tested, whereas Araldite

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