An investigation of the effects of aerodynamic heating on the flut¬ter of multibay external-skin panels has been carried out at a Mach num¬ber of 3.0 in the Langley 9- by 6-foot thermal structures tunnel. Both aluminum-alloy and 17-7 PH stainless-steel panels with a length-width ratio of 10 for each bay were tested at dynamic pressures between 1,500 psf and 5,000 psf and at stagnation temperatures up to 660° F. In addition, a few tests were made on the lower vertical stabilizer of the X-15 airplane which has external-skin panels unsupported for a length 10 times the width.nAll panels showed flutter boundaries characterized by an increase in panel thickness required to prevent flutter with increasing thermally induced stress prior to buckling. After buckling the panels showed flutter boundaries characterized by a decrease in thickness required to prevent flutter with further increases in thermal stress. The largest thickness required to prevent flutter in the presence of aerodynamic heating occurred at the transition between the flat-panel boundary and the buckled-panel boundary. This peak value (for aluminum-alloy panel) was as much as 60 percent greater than the extrapolated value for an unheated, unloaded panel.nValues of the modified-thickness-ratio flutter parameter for the unstressed panels (obtained by extrapolation) were in fair agreement for the aluminum, steel, and X-15 stabilizer panels. Peak values at transi-tion, however, showed large differences due to apparently minor changes in panel-support construction and/or changes in panel-skin material.
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