Analysis of crack-arrest design features for adhesively bonded composite joints: An experimental and numerical study

• Published in: Composite structures 2021-10, Vol.274, p.114301, Article 114301
• Main Authors: Sachse, R., Pickett, A.K., Middendorf, P.
• Format: Article
• Language: English
• Subjects: Adhesive joints; Crack-arrest; Damage tolerance; Fatigue crack growth; Numerical simulation
• ISSN: 0263-8223; 1879-1085
• DOI: 10.1016/j.compstruct.2021.114301

•An arrested-growth certification approach for adhesively bonded primary aircraft structures is discussed.•Mechanical design features are successfully applied to arrest fatigue crack growth in adhesively bonded joints.•Crack-arrest mechanisms are identified and a methodology to quantify them is presented.•A simulation method to model fatigue crack growth and crack-arrest suitable for an industry design process is presented. In this paper a systematic experimental and numerical study on mechanical design features to arrest fatigue crack growth in adhesive joints is performed. A material model for fatigue crack growth analysis based on a cohesive zone element formulation is presented together with a methodology to compare design features and to identify and quantify fundamental crack-arrest mechanisms. Results show that the influence of crack-arrest design features on fatigue crack growth can be successfully modelled using the developed material models and a mesoscopic representation of design features. A combination of reduced crack front loading via local reinforcement and Mode I reduction from through-thickness reinforcement are necessary to efficiently arrest crack growth. A simple local reduction of peel stresses does not lead to a sustainable crack-arrest and should therefore be avoided. Additionally, the two-dimensional growth of a crack in an adhesive joint can be exploited by increasing the effective crack front length. Finally, it is shown that a compression preload applied to the mechanical design features introduces through-thickness stresses to the adhesive that significantly reduce local fatigue crack growth rates.