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From:
http://eml.ou.edu/gramoll/Research/buckling.htm
University of Oklahoma Engineering Media Lab, Professor Kurt Gramoll
"Buckling Strength of Composite Lattice Structures", research by An Hou
The buckling strength of composite lattice cylindrical and conical shells under axial compressive loads is investigated. The lattice structures are composed of circumferential and helical members, whose cross-sections are rectangular. This research investigates the buckling behavior of both cylindrical and conical composite lattice structures and new design constraints for the most weight efficient structure with the highest buckling load.
The main emphasis is placed on the effects of geometrical configuration of the structure and the manufacturing process. It is observed that the effects of geometrical configuration are the winding angle, the slenderness of a member and the inertial properties of the members cross sections. The manufacturing process includes automated winding, winding path control, bridging effects and the effect of tension force. It is shown that these structures can be constructed by filament winding, the process can be automated, and the manufacturing costs can be reduced.
Numerical results are obtained by finite element analysis which are compared with experimental data and simplified analytical solutions. The motivation of the present work is to find the optimal winding pattern which filament winding can be easily applied and provides the highest strength to weight ratio. The problems caused during the fabrication process are also discussed. The buckling shapes predicted by the finite element analysis and the assumptions which were used in the theoretical and finite element analysis were verified by experimental tests. The buckling behavior, the geometric factors of structures and the fabrication process are fully investigated and developed. The final result of this research includes the numerical and experimental analysis of composite lattice cylindrical and conical shells via filament-winding. This provides a full understanding of composite lattice structures and can prove to be helpful in preliminary design of such structures.
Thin, cylindrical shells have been used extensively as load bearing structures, especially in the aerospace industry. Because of this, the stability of cylindrical structures subjected to external loads is a critical structural problem for rocket design, pressure vessels, rocket motor cases, gas tanks and aircraft pressure sources. Elastic instability will cause buckling and eventually lead to catastrophic failure of the structure. Thus it is important to show that the latticed structure fabricated by filament winding has uniform properties and can be applied to actual structures.
Carbon/epoxy composite materials have been used in upper stage structures of satellite launch vehicles in order to improve payload capability in Japan. The third stage structures of the H-1 and H-2 launch vehicles are triangular lattice cylinders which employ carbon fiber reinforced plastics (CFRP). One structure, called payload attach fitting (PAF), is used for connecting the satellites and the third stage motors, and the other, called motor attach fitting (MAF), is used for connecting the third stage motors and the spintables of the launch vehicles.
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