Abstract This study presents closed-form solutions for the critical buckling pressures and characteristic frequencies of underwater composite cylinders. The analytical solutions were derived using the full stiffness definitions from composite laminate theory, making them suitable for symmetric, asymmetric, hybrid, and/or double-shell (sandwich) cylindrical composite structures. These closed-form solutions were developed for critical buckling pressures in a hydrostatic environment as well as for critical buckling energy in a dynamic environment with combined hydrostatic and transient loads. Also, the characteristic frequencies were derived for a submerged and pressurized environment to account for added fluid mass and hydrostatic pressures. Computational and experimental data were used to validate the derived analytical work. The resulting solutions for critical buckling pressures agreed with numerical and experimental results for single-shell cylindrical structures. Moreover, for double-shell cylindrical structures with foam cores (sandwich structures), the collapse pressure is shown to be proportional to the core’s transverse shear modulus. The solutions were suitable for predicting the collapse pressure for sandwich structures with relatively low-density cores. Lastly, solutions for estimating the energy emitted during an implosion event and the energy required for buckling in sub-critical pressure environments were also derived and validated with the experimental data.

中文翻译：

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水下复合气瓶的屈曲、振动和能量解决方案

摘要 本研究提出了水下复合圆柱体的临界屈曲压力和特征频率的封闭形式解决方案。解析解是使用复合层压板理论中的全刚度定义推导出来的，使其适用于对称、非对称、混合和/或双壳（夹心）圆柱复合结构。这些封闭形式的解决方案是为流体静力环境中的临界屈曲压力以及具有组合流体静力和瞬态载荷的动态环境中的临界屈曲能量而开发的。此外，特征频率是针对水下和加压环境推导出来的，以说明增加的流体质量和静水压力。计算和实验数据用于验证派生的分析工作。临界屈曲压力的结果解与单壳圆柱结构的数值和实验结果一致。此外，对于具有泡沫芯（夹心结构）的双壳圆柱结构，坍塌压力与芯的横向剪切模量成正比。该解决方案适用于预测具有相对低密度芯的夹层结构的倒塌压力。最后，还推导出了用于估算内爆事件期间发出的能量和亚临界压力环境中屈曲所需能量的解决方案，并使用实验数据进行了验证。对于具有泡沫芯的双壳圆柱结构（夹心结构），显示坍塌压力与芯的横向剪切模量成正比。该解决方案适用于预测具有相对低密度芯的夹层结构的倒塌压力。最后，还推导出了用于估算内爆事件期间发出的能量和亚临界压力环境中屈曲所需能量的解决方案，并使用实验数据进行了验证。对于具有泡沫芯的双壳圆柱结构（夹心结构），显示坍塌压力与芯的横向剪切模量成正比。该解决方案适用于预测具有相对低密度芯的夹层结构的倒塌压力。最后，还推导出了用于估算内爆事件期间发出的能量和亚临界压力环境中屈曲所需能量的解决方案，并使用实验数据进行了验证。