The use of high polymer composite materials in aircraft requires the incorporation of viscoelastic effects during the design process to fully capture the capabilities of these materials. One design analysis of concern is the prediction of flutter for an aircraft wing because flutter may result in the catastrophic failure of the wing. The current analysis assumes that the wing material is elastic which neglects the time dependent memory effect that appears for viscoelastic materials such as polymer composites. Previous work has shown that the viscoelastic effects lead to a flutter time in addition to a flutter speed. This earlier time to flutter theory was limited to constant flight speeds during the analysis so the effects of past maneuvers and mission profiles could not be explored. An expanded theory using an operator mapping is possible and captures the effects of maneuvers. Further, the theory is implemented in Matlab to provide numerical examples using a viscoelastic Goland wing. The results show that the time to flutter for most scenarios is limited to twice the relaxation period of the material, and that the results are sensitive to the functions used to represent the changes in flight velocity. Time to flutter decreases with increasing flight cycles, suggesting a trend similar to the fatigue limit of metals. For the viscoelastic Goland wing considered, 50,000 flight cycles per relaxation period is the maximum limit before flutter occurs instantaneously for a range flight velocities and viscosities.

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Conference 57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2016
Citation
Merrett, C. (2016). Time to flutter of a maneuvering viscoelastic Goland wing. Presented at the 57th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2016.