Hydrostatic Testing and Analysis of Graphite-Epoxy Cylinders.

摘要

An experimental study was conducted to investigate the use of advanced composite materials in unstiffened thin-walled cylindrical structures subjected to hydrostatic pressure. Specifically, graphite/epoxy was looked at for potential application for small submersible pressure hulls. The investigation concentrated on the fabrication, instrumentation, testing, and evaluation of several 12-ply graphite/epoxy cylinders of four different laminate configurations. The test specimens were 18 inches long with radii of 2.76 inches, and each was instrumented with 8 circumferentially and 2 axially mounted strain gages. Data collected from the strain gages throughout the tests were used in a modified Southwell type analysis and an analysis to deduce the buckling mode shape. The Southwell analysis method was shown to have a valid applicability to the buckling of laminated fiber-reinforced composite pressure vessels. A method was developed to use the bending strain data at locations around the centerline of the specimen to deduce the number of, circumferential buckling waves. In addition, 1/2 inch ring specimen were cut from the excess ends of each specimen and tested under two-point compression, yielding information about the material properties of the laminates as fabricated. The hydrostatic tests were designed to verify the results of an analytical and numerical study that was conducted to determine the optimal laminate stacking sequences for buckling considerations. The test results indicate that the classical solution method presented by R.M. Jones produced accurate predictions of buckling strengths and correct relative rankings of the different laminate types.