Stability Analysis And Design Optimization Of Typical Spacecraft Structures

Sandwich plates and stiffened cylindrical shells have been widely used in aerospace, machinery, civil engineering, and marine engineering for their high specific strength and specific rigidity. For aerospace practice, they are the main load-bearing components of launch vehicles and missiles. During their service time, these components'main working conditions contain inertia force, counterforce by adjacent segments and dynamic force. And for some submerged bodies, they even face great impact pressure that arises from the collapsing bubbles. The main failure mode can be buckling caused by compression rather than intensity damage. Therefore, lightweight designs of stiffened cylindrical shell structure and fairing considering maximizing the critical buckling load have important engineering significant. The main works of this thesis are as follows:1 The stability analysis methods and optimization method are discussed in details and their pros and cons are compared. This provides a theoretical support for the following design of stiffened cylindrical shell segments and sandwich structure fairing.2 A two-step optimization method is proposed for stiffened cylindrical shell structures subjected to non-uniform distribution of external pressure loading. The optimization to make the grids distribute evenly under hydrostatic pressures is carried out firstly with the number and size of stiffeners as the design variables. Then the local hierarchical stiffener optimization and regional stiffener optimization are carried out, during which the non-uniform distribution of external pressure load are imposed and the first optimization results are set as lower bounds of the design variables. The final optimization results can be used as a reference for engineering design.3 The stability analysis and optimization of large size fairing with honeycomb sandwich are given. The numerical model of sandwich structure fairing is established based on the honeycomb core's equivalent theory in ABAQUS. Then the optimization which considering both the stability and structure mass is carried out with the honeycomb's size, composite panels' numbers and angles as the design variables The results which satisfy engineering requirements can be used as a reference for the following design.