REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

FLUTTER ANALYSIS of MISSILE COMPOSITE FOLDING FINS

Mirko Dinulović

Faculty of Mechanical Engineering, University of Belgrade, Serbia, mdinulovic@mas.bg.ac.rs

Boško Rašuo

Faculty of Mechanical Engineering, University of Belgrade, Serbia, brasuo@mas.bg.ac.rs

Branimir Krstić

Military Academy, University of Defense in Belgrade, Serbia, branimir.krstic@va.mod.gov.rs

Predrag Andrić

Military Academy, University of Defense in Belgrade, Serbia, andricp@gmail.com

Abstract: The “flutter” of missile stabilizers (fins) is a serious cause of stability loss and flight vehicle failure. It involves the unfavorable interaction of aerodynamic, elastic and inertia forces on structures to produce an unstable oscillation that often results in structural failure. High-speed aircraft are most susceptible to flutter. In the present paper the flutter phenomenon on composite folding missile fins is investigated. Two degrees of freedom (plunge and twist) analytical model of representative fin airfoil section is presented. Based on this model the critical flutter speed for the composite folding missile fin is calculated for subsonic flight conditions. Determination of natural fin frequencies (in bending and twisting) is calculated using finite element approach by 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. Complete numerical fin flutter model consisted of structural fin model and aerodynamic model interconnected with surface splines. Several aerodynamic theories (doublet-lattice, strip theory and piston theory) are discussed and their application to flutter speed calculation is analyzed.

Keywords: flutter, composites, missile stabilizer, folding fin.