Free vibration response behavior of laminated composite hybrid and Glass Fiber Reinforced Plastic (GFRP) shells is analyzed using a modified higher order zigzag theory (HOZT). The laminated shell model is developed by considering the thickness co-ordinate to radius of curvature ratio (z/R) as well as zero shear conditions at free surfaces of the shell. The C⁰ finite element formulations with nine-noded quadrilateral isoparametric shell element having seven degrees of freedom per node are adopted to compute the natural frequency of the shells. The hybrid laminate is modeled by placing carbon fibers in the outermost layers and glass fibers in the rest to improve the flexural behavior of the shell. Experimental studies are performed to find out the mechanical properties of hybrid and GFRP laminates such as Young modulus, shear modulus and poison's ratio. The experimental procedure of free vibration is carried out by Bruel & Kjaer (B&K) modal analysis instruments along with RT Pro modal analysis software and the results are compared with the theoretical findings. Moreover the present theoretical results have been examined by comparing with 2D solutions as well as 3D elasticity solutions available in the published literature to verify the accuracy of the present HOZT. An extensive parametric study on laminated composite hybrid and GFRP shells with various laminations is undertaken to investigate the effect of reinforcement scheme on the free vibration behavior of such laminated shells.

使用改进的高阶之字形理论（HOZT）分析了层压复合材料杂化材料和玻璃纤维增​​强塑料（GFRP）壳体的自由振动响应行为。通过考虑厚度坐标与曲率半径之比（z / R）以及在壳的自由表面处的零剪切条件来开发叠层壳模型。碳⁰采用具有每个节点七个自由度的九节点四边形等参壳单元的有限元公式来计算壳的固有频率。通过将碳纤维放置在最外层，将玻璃纤维放置在其余的层中，以改善壳体的挠曲性能，可以对混合层压板进行建模。进行实验研究以找出混合和GFRP层压板的机械性能，例如杨氏模量，剪切模量和毒物比。自由振动的实验过程是通过Bruel＆Kjaer（B＆K）模态分析仪器以及RT Pro模态分析软件进行的，并将结果与​​理论结果进行了比较。此外，已经通过与公开文献中可用的2D解决方案以及3D弹性解决方案进行比较来检验当前的理论结果，以验证当前HOZT的准确性。进行了广泛的参数研究，研究了多层复合材料和多层复合材料GFRP壳，以研究增强方案对此类壳的自由振动行为的影响。