On the impact of delamination on composite structures: comprehensive modal, static, and buckling analysis

Abstract

Research on composite materials has gained prominence due to their excellent mechanical properties combined with low weight, attracting various engineering fields such as aerospace, naval, automotive, and industrial engineering. Historically, challenges involving composite materials include understanding their characteristics, controlling quality, and optimizing properties. With the advancement of computational capacity, the finite element method has become an essential tool for predicting the behavior of these materials under different boundary conditions. This specific study focuses on thin-walled cylinders composed of 10-layer shells with various delaminations. Each tube was subjected to three types of analyses: modal, static, and buckling. The detailed analysis of these delaminated structures aims to understand how delamination parameters affect structural performance, allowing the development of more failure-tolerant designs. The parameters considered for simulating delamination include: z (height of the delamination in the ellipse), b (major axis of the ellipse), r (ratio between the major and minor axes of the ellipse), θ (angle of inclination of the ellipse), α (severity of the delamination), and n (layer of the thin wall with the delamination). A total of 1000 tests were conducted for each type of analysis with the same delaminations. The responses obtained—natural frequency, inverse Tsai Wu index, and eigenvalue—did not show a significant correlation among themselves, except for a good internal correlation of the eigenvalues. To better understand the impact of each variable on the obtained responses, the Sobol index, a global sensitivity analysis technique, was used. This analysis helped identify the most critical parameters influencing each type of response. The results indicate that, although there is no direct and universal correlation among all the analyzed responses, a detailed understanding of the influence of each delamination parameter can guide the development of more robust and resilient designs. The findings of this study are valuable for materials engineering, contributing to advances in the safety and efficiency of composite structures. Finally, the thesis concludes that the use of modal, static, and buckling analyses combined with sensitivity analysis is an effective approach to evaluate and improve the performance of delaminated composite structures, providing important insights for future projects and research in the field.