보강된 복합재 압력선체의 좌굴과 파손양상에 관한 연구

Abstract

The objective of this study is to predict structural characteristics of composite pressure hulls with isotropic stiffeners using finite element analysis. The buckling and failure on the pressure hull are estimated by static and eigen buckling analysis.

The pressure hull has stiffened cylindrical shell structure to resist a high hydraulic pressure, and spherical or cylindrical shell is attached to both ends. Cylindrical shell is the most common structure like ship, submarine, and torpedo. In particular, buckling occurs at a much lower stress than material strength when the shell is subject to pressure load. The structure built with metals requires 45% of buoyancy for its own hull weight and is called weight-sensitive structure. Therefore, many studies have been performed so far on analyzing such shell structure and many shell theories have been suggested subsequently.

However, the clear study of the stiffener is made by composite material in isotropic cylindrical stiffeners did not proceed. Therefore, by applying the isotropic reinforcing material in the composite cylindrical shell, it was evaluated against buckling and failure for an efficient design.

When the stiffener spacing is increased, or the flange thickness is reduced, the buckling pressure is decreased. However, it was confirmed that the failure pressure is constant regardless of the shape parameters.

If gaps between stiffeners are increased and the thickness of the cylindrical shell is thin relatively, local buckling with irregular lobes is occurred, due to the instability of shells. This is subject to the ratio that is diameter(D) of the stiffener gaps(L). Therefore, the factor should be considered in the design phase sufficiently.

Generally, if a global buckling is occurred, the buckling pressure is lower than the failure pressure. However, the opposite results were obtained this analysis results. Therefore, when the composite cylindrical shell design, both a buckling pressure and a failure pressure should be considered to a design pressure.