The sandwich structures are three- or multilayered structures such that their mechanical properties are better than each single layer. In the current research, a three-layered cylindrical shell including a functionally graded porous core and two reinforced nanocomposite face sheets resting on the Pasternak foundation is used as model to provide a comprehensive understanding of vibrational behavior of such structures. The core is made of limestone, while the epoxy is utilized as the top and bottom layers’ matrix phase and also it is reinforced by the graphene nanoplatelets (GNPs). The pattern of the GNPs dispersion and the pores distribution play a crucial role at the continuous change of the layers’ properties. The sinusoidal shear deformation shells theory and the Hamilton’s principle are employed to derive the equations of motion for the mentioned cylindrical sandwich shell. Ultimately, the impacts of the model’s geometry, foundation moduli, mode number, and deviatory radius on the vibrational behavior are investigated and discussed. It is revealed that the natural frequency and rotation angle of the sandwich shell are directly related. Moreover, mid-radius to thickness ratio enhancement results in the natural frequency reduction. The results of this study can be helpful for the future investigations in such a broad context. Furthermore, for the pipe factories current study can be effective at their designing procedure.

中文翻译：

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湿热环境下夹心圆柱壳的振动分析

夹层结构为三层或多层结构，其力学性能优于单层结构。在目前的研究中，一个三层圆柱壳包括一个功能梯度多孔核和两个位于 Pasternak 基础上的增强纳米复合材料面板，被用作模型，以全面了解此类结构的振动行为。核心由石灰石制成，而环氧树脂用作顶层和底层的基体相，并由石墨烯纳米片 (GNP) 增强。GNPs 的分散模式和孔隙分布在层的性能不断变化中起着至关重要的作用。采用正弦剪切变形壳理论和哈密顿原理推导出上述圆柱形夹心壳的运动方程。最后，研究和讨论了模型的几何形状、基础模量、模态数和偏心半径对振动行为的影响。结果表明，夹层壳的固有频率和旋转角直接相关。此外，中半径与厚度比的增强导致固有频率降低。这项研究的结果有助于在如此广泛的背景下进行未来的调查。此外，对于管厂来说，当前的研究在他们的设计过程中是有效的。和偏差半径对振动行为的研究和讨论。结果表明，夹层壳的固有频率和旋转角直接相关。此外，中半径与厚度比的增强导致固有频率降低。这项研究的结果有助于在如此广泛的背景下进行未来的调查。此外，对于管厂来说，当前的研究在他们的设计过程中是有效的。和偏差半径对振动行为的研究和讨论。结果表明，夹层壳的固有频率和旋转角直接相关。此外，中半径与厚度比的增强导致固有频率降低。这项研究的结果有助于在如此广泛的背景下进行未来的调查。此外，对于管厂来说，当前的研究在他们的设计过程中是有效的。