Instability of delamination growth in buckled stiffened composite panels

• Buckling and delamination growth interaction by means of numerical models able to capture related nonlinear dynamic phenomena. • SMart time XB (SMXB) methodology is able to predict dynamic unstable delamination growth even by static analyses. • The study presents validation of the method by experimental data showing excellent agreement with experimental results. • The sensitivity to initial delamination size reveals the length of the damage to have a significant impact on growth results. The interaction between delamination propagation and buckling shape in composite structures becomes particularly significant in the presence of dynamic phenomena. This type of behaviour is fundamental to be understood in the design and analysis of structures, and is highly relevant research for composite materials, supported by fundamental approaches from mechanics, materials science and engineering. In particular, the sudden switching of buckling modes intensifies the influence of buckling on delamination growth, leading to a more rapid and complex evolution of damage. This study investigates the interaction between dynamic buckling and delamination propagation in a composite-stiffened panel using the SMart time XB (SMXB) tool, an innovative and robust numerical methodology for simulating damage propagation. The numerical simulation of this phenomenon is compared to both static and transient analyses. The structure consists of a stiffened composite panel with an omega-section stringer, including an artificial delamination to simulate an initial debonding. The study comprises a validation phase based on experimental data already published in the literature. Furthermore, the study aims to validate the SMXB procedure for simulating dynamic phenomena through non-linear static simulations, without inertia effects and convergence issues, to assess its effectiveness in capturing unstable delamination propagation.