Significance of Wash-Out on the Flutter Characteristics of Composite Wings

摘要

Figure 1 shows the variation of the nondimensional flutter speed, i.e., V_F/bω_α against x_α for three different positive values of ψ, i.e., ψ = +0.2, +0.4, and +0.6, which induce the desired wash-out effect. Several representative values of the frequency ratio ω_h/ω_α were used in obtaining the results as shown in the figure. For comparison purposes, results for negative values of ψ, i.e., for ψ = -0.2, -0.4, and -0.6, are shown in Fig. 2. (It should be noted that the values of x_α plotted in Figs. 1 and 2 are all negative so that the mass axis is behind the elastic axis, which is usually the case.) The density ratio m/πρb~2 and the radius of gyration defined as r_α = (I_α/mb~2)~(1/2) were kept constant at 20 and 0.5, respectively, for all cases. The elastic axis location was assumed to be 20% of the semichord and forward of the midchord position, i.e., a = —0.2. The first three normal modes were used in the flutter analysis and were subsequently found to be adequate.