부산대학교 도서관

An out-of-plane displacement analysis is conducted on a circular composite disk in which a pre-stressed condition is created by clamping the specimen along a tapered boundary. This configuration is designed to lower the boundary stresses when uniform pressures are subsequently applied during permeability tests developed to study potential microcracking and permeability resistant material systems for cryogenic tank usage. A finite element analysis of the pre-stressed condition predicted a displacement field in which the location of the maximum out-of-plane displacement did not coincide with the principal material coordinate system despite the fact that the specimen was symmetric with respect to its mid-plane and uniformly clamped around the boundary. This was attributed to variations in the terms contained in the bending stiffness matrix which were shown to change as a function of the angle measured relative to the principal material directions. The finding was investigated by using the method of speckle metrology and digital image correlation to experimentally measure the displacement field. A comparison between the experimental and analytical results showed a very good agreement, thereby validating the finite element model and its prediction.