Abstract
The fundamental frequencies of thin-walled elliptical composite cylinders wherein the fiber orientation in some or all of the layers varies linearly from the flattest region of the cross section to the most curved region of the cross section are discussed. The study is motivate by previous work which demostrated that such a variable fiber orientation scheme improved the axial buckling capacity of elliptical composite cylinders relative to a baseline quasi-isotropic elliptical cylinders. The improved axial buckling capacity approached the axial buckling capacity of the so-called equivalent quasi-isotopic circular cylinder, which decreases as the cross section is made elliptical. At issue is the degree to which the vibration behavior of composite elliptical cylinders is impacted by having the fiber orientation vary with circumferential location. However, the answer to this question is discussed in the context of two broader issues, namely, determining to what degree is the fundamental frequency of a circular cylinder is changed if the cross section is made elliptical, and investigating if there are any advantages as regards fundamental frequency vibration response to varying fiber angle, and therefore the wall stiffness characteristics, with circumferential location. For an elliptical cylinder the radius of curvarture varies with circumferential location, so varying wall stiffness with circumferential location might couple in a positive fashion. The results, which are based on finite element models of the elliptical and circular cylinders, indicate that even for what is considered a significant range of fiber orientations that vary linearly with circumferential location, the fundamental frequencies of both elliptical and circular cylinders are not significantly influenced. On the other hand, the circumferential wave number is influenced.
Published Version
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