Title page for ETD etd-10242005-124101


Type of Document Dissertation
Author Fuchs, John Peter
URN etd-10242005-124101
Title Numerical and experimental investigation of the bending response of thin-walled composite cylinders
Degree PhD
Department Engineering Mechanics
Advisory Committee
Advisor Name Title
Hyer, Michael W. Committee Chair
Frederick, Daniel Committee Member
Griffin, Odis Hayden Jr. Committee Member
Grdal, Zafer Committee Member
Keywords
  • Cylinders
  • Flexure
Date of Defense 1993-09-05
Availability restricted
Abstract

A numerical and experimental investigation of the bending behavior of six eight-ply graphite-epoxy circular cylinders is presented. Bending is induced by applying a known end-rotation to each end of the cylinder, analogous to a beam in bending. The cylinders have a nominal radius of 6 inches, a length-to-radius ratio of 2 and 5, and a radius-to-thickness ratio of approximately 160. A [±45/0/90]S quasi-isotropic layup and two orthotropic layups, [±45/02]S and [±45/902]s, are studied. A geometrically nonlinear special-purpose analysis, based on Donnell's nonlinear shell equations, is developed to study the prebuckling responses and gain insight into the effects of non-ideal boundary conditions and initial geometric imperfections. A geometrically nonlinear finite element analysis is utilized to compare with the prebuckling solutions of the special-purpose analysis and to study the buckling and postbuckling responses of both geonletrically perfect and imperfect cylinders.

The imperfect cylinder geometries are represented by an analytical approximation of the measured shape imperfections. Extensive experimental data are obtained from quasistatic tests of the cylinders using a test fixture specifically designed for the present investigation.

A description of the test fixture is included. The experimental data are compared to predictions for both perfect and imperfect cylinder geometries. Prebuckling results are presented in the form of displacement and strain profiles. Buckling end-rotations, moments. and strains are reported, and predicted mode shapes are presented. Observed and predicted moment vs. end-rotation relations, deflection patterns. and strain profiles are illustrated for the postbuckling responses. It is found that a geometrically nonlinear boundary layer behavior characterizes the prebuckling responses. The boundary layer behavior is sensitive to laminate orthotropy, cylinder geometry, initial geometric imperfections, applied end-rotation, and non-ideal boundary conditions. Buckling end-rotations, strains, and moments are influenced by laminate orthotropy and initial geometric imperfections.

Measured buckling results correlate well with predictions for the geometrically imperfect specimens. The postbuckling analyses predict equilibrium paths with a number of scallop-shaped branches that correspond to unique deflection patterns. The observed postbuckling deflection patterns and measured strain profiles show striking similarities to the predictions in some cases. Ultimate failure of the cylinders is attributed to an interlaminar shear failure mode along the nodal lines of the postbuckling deflection patterns.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
[BTD] LD5655.V856_1993.F823.pdf 46.83 Mb 03:36:47 01:51:29 01:37:33 00:48:46 00:04:09
[BTD] next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.

Browse All Available ETDs by ( Author | Department )

dla home
etds imagebase journals news ereserve special collections
virgnia tech home contact dla university libraries

If you have questions or technical problems, please Contact DLA.