Non-linear Aeroelastic Oscillations in Curvilinear Fibre-Reinforced Composite Cylindrical Shells

Abstract

Purpose: This study investigates how curvilinear fibre paths in variable stiffness composite laminates (VSCLs) influence large-amplitude, non-linear aeroelastic oscillations—particularly limit-cycle oscillations (LCOs) and chaotic responses—of circular cylindrical shells under supersonic flow. The aim is to assess whether curvilinear fibre reinforcements offer stability and performance advantages over traditional straight-fibre laminates in post-flutter regimes. Methods: A new geometrically non-linear model for circular cylindrical shells reinforced by curvilinear fibres is developed. It uses Kirchhoff’s hypothesis and von Kármán strain–displacement relations, with the curvilinear fibre paths influencing the stiffness related terms. A single-element computational model incorporating polynomial and trigonometric basis functions enables efficient dynamic analysis. Linear stability is assessed via eigensolution routines, and post-flutter non-linear responses are obtained by time domain integration, where advantage is taken of the naturally reduced-order model. Results: The study finds that while the circumferential component of membrane inertia significantly affects certain vibration and flutter modes, longitudinal inertia can be neglected. Curvilinear fibre configurations delay flutter onset and modify the post-flutter response. Both LCOs and chaotic oscillations are observed, with curvilinear fibres shown to reduce oscillation amplitudes and lower frequency content in LCOs. Longitudinally travelling waves are identified and it is found that non-linear modal interaction is connected with chaotic behaviour. Conclusion: Curvilinear fibre orientations enhance the aeroelastic performance of cylindrical shells by extending the stable operating range before flutter occurs and by reducing the severity of post-flutter oscillations. These findings suggest that the use of curvilinear reinforcement fibres enables improvements in the non-linear dynamic behaviour of aerospace circular cylindrical thin structures.