Unstable Delamination Growth in Stiffened Composite Panels Under Cyclic Loading Conditions

first_pagesettingsOrder Article Reprints Open AccessArticle Unstable Delamination Growth in Stiffened Composite Panels Under Cyclic Loading Conditions by Rossana Castaldo 1,*,Angela Russo 1,Mauro Zarrelli 2ORCID,Cinzia Toscano 3 andAniello Riccio 1,2ORCID 1 Department of Engineering, University of Campania “Luigi Vanvitelli”, Via Roma 29, 81031 Aversa, Italy 2 IPCB Institute of Polymers, Composites and Biomaterials, CNR National Research Council, Piazza Granatello, 80055 Portici, Italy 3 CIRA, Centro Italiano Ricerche Aerospaziali, 81043 Capua, Italy * Author to whom correspondence should be addressed. Polymers 2024, 16(22), 3118; https://doi.org/10.3390/polym16223118 Submission received: 23 September 2024 / Revised: 26 October 2024 / Accepted: 5 November 2024 / Published: 7 November 2024 (This article belongs to the Special Issue Mechanical Characterization of Polymer Composites) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract Aeronautical structures can be damaged by objects during operation and maintenance. Indeed, foreign object impacts (FOIs) affect the overall performance of composite structural components. Delamination is the most critical damage mechanism as it is undetectable and develops silently. This phenomenon can be worsened by cyclic loading, as residual strength and stiffness can decrease rapidly, potentially leading to collapse. Unstable delamination growth is critical because it can occur without an increase in the applied load, threatening the integrity of the structure. Predicting this behaviour under fatigue loading is challenging for standard non-linear finite element methods (FEMs), which often face convergence problems when simulating the dynamic nature of delamination growth. This paper presents an efficient alternative methodology for analysing the propagation of delamination under cyclic loading in composite structures, with non-linear static analyses. This new methodology has been shown to be able to correctly account for the decrease in load carrying capacity during growth by performing ad hoc iterations with alternating force and displacement-controlled FEM simulations. To achieve this objective, the Paris law approach has been implemented in the ANSYS FEM code together with an enhanced virtual crack closure technique (VCCT)-based method. The model correctly predicted delamination growth in stiffened aeronautical panels with artificial delaminations subjected to cyclic compression loading.