Aeroelastic optimization of a helicopter rotor with two-cell composite blades

Aeroelastic and sensitivity analyses of the rotor based on a finite element in space and time are linked to an automated optimization algorithm to perform optimization studies for a four-bladed, soft in-plane composite rotor consisting of a two-cell thin-walled beam. The design variables used in this study are the ply angles of the laminated walls of the composite beam. The objective function minimizes the 4/rev hub loads, with constraints on blade frequencies and aeroelastic stability in forward flight. Optimum design solutions show a reduction in the objective function of about 20% due to elastic stiffnesses and an additional 13% due to composite couplings. Starting from an initially infeasible design, the optimum design solution with negative lag bending-torsion coupling results in an increase in lag mode damping of about 140% compared to the baseline layup. c* c* c* ^d-> ^/> ^m CT c

[1]  Inderjit Chopra,et al.  Aeroelastic optimization of a helicopter rotor , 1989 .

[2]  E. Smith,et al.  Formulation and evaluation of an analytical model for composite box-beams , 1991 .

[3]  G. Vanderplaats.  Approximation concepts for numerical airfoil optimization , 1979 .

[4]  Peretz P. Friedmann,et al.  Structural optimization with aeroelastic constraints of rotor blades with straight and swept tips , 1990 .

[5]  Inderjit Chopra,et al.  Aeroelastic optimization of a helicopter rotor with composite coupling , 1995 .

[6]  Inderjit Chopra,et al.  Aeroelastic optimization of a helicopter rotor to reduce vibration and dynamic stresses , 1996 .

[7]  Peretz P. Friedmann,et al.  Helicopter vibration reduction using structural optimization with aeroelastic/multidisciplinary constraints - A survey , 1991 .

[8]  E. Smith,et al.  Air and ground resonance of helicopters with elastically tailored composite rotor blades , 1993 .

[9]  Edward C. Smith,et al.  Aeroelastic response, loads, and stability of a composite rotor in forward flight , 1993 .

[10]  Mark W. Davis,et al.  Helicopter rotor dynamics optimization with experimental verification , 1991 .

[11]  Mark W. Nixon,et al.  Dynamic analysis of pretwisted elastically-coupled rotor blades , 1994 .

[12]  M. Scully,et al.  Computation of helicopter rotor wake geometry and its influence on rotor harmonic airloads , 1975 .

[13]  Inderjit Chopra,et al.  Aeroelastic optimization of a helicopter rotor using an efficient sensitivity analysis , 1990 .

[14]  Inderjit Chopra,et al.  Structural behavior of two-cell composite rotor blades with elastic couplings , 1991 .

[15]  Peretz P. Friedmann,et al.  Vibration analysis of composite turbopropellers using a nonlinear beam-type finite-element approach , 1989 .

[16]  A. J. Morris,et al.  A multicriteria objective function optimization scheme for laminated composites for use in multilevel structural optimization schemes , 1987 .

[17]  Garret N. Vanderplaats,et al.  CONMIN: A FORTRAN program for constrained function minimization: User's manual , 1973 .