Design of commercial aircraft structure, composed of composite material, requires the
prediction of failure loads given large scale damage. In particular, a fuselage of
graphite/epoxy lamination was analyzed for damage tolerance given a standard large
crack that severed both skin and internal structure. Upon loading, a zone of damage is
known to develop in front of a crack-tip in composite laminates; and, its material
behavior within the damage zone is characterized as strain softening. This investigation
sought to develop a computational model that simulates progressive damage growth and
predicts failure of complex laminated shell structures subject to combined tensile and
flexural load conditions. This was accomplished by assuming a macroscopic definition
of orthotropic damage that is allowed to vary linearly through the shell thickness. It was
further proposed that nonlocal plate strain and curvature act to force damage growth
according to a set of uniaxial criteria. Damage induced strain softening is exhibited by
degradation of laminate stiffness. An expression for the damage reduced laminated
plate stiffness was derived which assumed the familiar laminated plate [AM] stiffness
matrix format. The model was implemented in a finite element shell program for
simulation of fracture and evaluation of damage tolerance. Laminates were characterized
for damage resistance according to material parameters defining nonlocal strain and
the damage growth criteria. These parameters were selected using an inverse method to
correlate simulation with uniaxial strength and fracture test results. A novel combined
tension-plus-flexure fracture test was developed to facilitate this effort. Analysis was
performed on a section of pressurized composite fuselage containing a large crack.
Good agreement was found between calculations and test results. / Graduation date: 1998
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34015 |
| Date | 02 July 1997 |
| Creators | Nahan, Matthew F. |
| Contributors | Kennedy, Timothy C. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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