Vibration characteristics and response behaviors of three-dimensional-four-directional knitted composite sandwich cylindrical shells with pyramidal latticed cellular cores

Responding to the stringent lightweight and mechanical performance requirements of aerospace vehicle devices, a novel sandwich cylindrical shell structure with three-dimensional-four-directional knitted composite skins and pyramidal latticed cellular cores is tailored as a well-optioned scheme for the critical components. A desired dynamic model of the goal structure under free and forced vibration occasions is proposed first as a prediction tool for coping with the existing lack, and the virtual spring technique is filled in the developed model to extend arbitrary boundary conditions. In the framework of the theoretical formulations constructed, explicit expressions for the effective mechanical properties of spatially knitted composite skins and cellular cores are derived. Afterwards, the first-order shear deformation shell theory and Jacobi-Ritz approach are utilized to deduce energy expressions, and the mode shapes, inherent frequencies, response amplitude, and decay signature are solved by adopting the eigenvalue and Newmark-Beta techniques. Compliant model parameters with low running costs and guaranteed calculation precision are given in convergence analyses, which pave the path for efficient data output and numerical calibration. After undertaking the model validation work, the impact laws of key variables on the dynamic indicators are released, with some contributions being made conducive to upgrading the vibration resistance capabilities.