Preliminary modal analysis of inflatable wings

Comparisons between experimentally determined natural frequencies and mode shapes of an inflatable wing and finite element predictions of those natural frequencies and mode shapes are presented in this paper. Traditional modal test methods were used to determine the vibrational characteristics of the wing. Both linear and non-linear finite element methods have been used to predict natural frequencies and mode shapes, with comparisons between these methods presented herein. A wing constructed of an external restraint made of Vectran fabric encasing a polyurethane bladder is considered for internal pressures ranging from 5 to 25 psig. Though the finite element predictions presented herein conclude the current model is generally too stiff in predicting natural frequencies, the results are promising for an initial analysis of this unique structural system.