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Approximate Buckling Analysis for Orthotropic Rectangular Panels with centrally Located Cutouts

An approximate analysis for predicting buckling
of rectangular orthotropic composite plates with cen-
trally located cutouts is presented. In this analysis,
the prebuckling and buckling problems are converted
from a two-dimensional to a one-dimensional system
of linear differential equations with variable coeffi-
cients. The conversion is accomplished by expressing
the displacements as series with each element con—
taining a trigonometric function of one coordinate
and a coefficient that is an arbitrary function of the
other coordinate. Ordinary differential equations are
then obtained from a variational principle.

Analytical results obtained from the approximate
analysis are compared with finite element analy-
ses for isotropic plates and for [010]S, [9010]S, and
[(0/90)5]s specially orthotropic plates with central
circular cutouts of various sizes. Experimental re-
sults for the specially orthotropic plates are also pre—
sented. In nearly all cases, the approximate analysis
predicts the buckling mode shapes correctly and pre-
dicts the buckling loads to within a few percent of
the finite element and experimental results.

In aircraft and spacecraft structures, cutouts are
commonly found as access ports for mechanical and
electrical systems. Often during flight, structural
members with cutouts experience compression loads,
and thus the ability of a compression member with
a cutout to resist buckling is important in design.
Several studies of the elastic buckling behavior of
isotropic square plates containing central circular
cutouts have been presented in the technical litera-
ture. Reference 1 presents a summary of these stud—
ies. Substantially fewer studies (e.g., refs. 1—3) of the
elastic buckling behavior of rectangular laminated
composite plates with cutouts appear in the technical
literature. Understanding the buckling behavior of a
rectangular composite plate with a centrally located
traction-free cutout provides valuable insight into the
behavior of more complicated structural members.