The analysis of laminate lay-up effect on the flutter speed of composite stabilizers

Abstract

This paper presents an analytical study on the effect of laminate lay-up of composite missile stabilizer structure for achieving a maximum flutter speed without strength penalty. The flexible stabilizer structure in high-velocity flow may experience flutter, an aeroelastic phenomena where vibrations of the structure become unstable and can cause stability loss and flight vehicle failure. Flutter in missiles is mainly affected by the aerodynamic and structural properties of the stabilizers whereas flight vehicle body has a minor role. In the present paper the effect of laminate lay-up on flutter speed of composite missile stabilizers is investigated. Two degrees of freedom (plunge and twist) analytical model of typical fin stabilizer airfoil section is presented. Based on this model the critical flutter speed for the composite missile stabilizer is derived for subsonic flight conditions. It was found that natural stabilizer frequencies (in bending and twisting) highly influence the maximum flutter speed. Natural fin frequencies (in bending and twisting) are calculated using finite element approach based on Lanczos method of frequencies extraction. Several modal frequency models are investigated and results are discussed, since the accurate prediction of natural frequencies plays significant role in overall flutter speed (VF) determination. For the trapezoidal stabilizer shape different laminate lay-up sequences are investigated, flutter speeds calculated and results compared in order to determine maximum flutter speed. The material of interest in this study was carbon based AS/4-3501-6.