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Buckling Behavior of Compression-Loaded Quasi-Isotropic Curved Panels with a Circular Cutout

Abstract

Results from a numerical and experimental study of
the response of compression-loaded quasi-isotropic
curved panels with a centrally located circular cutout are
presented. The numerical results were obtained by using
a geometrically nonlinear finite element analysis code.
The effects of cutout size, panel curvature and initial geo-
metric imperfections on the overall response of compres-
sion-loaded panels are described. In addition, results are
presented from a numerical parametric study that indicate
the effects of elastic circumferential edge restraints on the
prebuckling and buckling response of a selected panel and
these numerical results are compared to experimentally
measured results. These restraints are used to identify the
effects of circumferential edge restraints that are intro-
duced by the test fixture that was used in the present study.
It is shown that circumferential edge restraints can intro-
duce substantial nonlinear prebuckling deformations into
shallow compression-loaded curved panels that can re-
sults in a significant increase in buckling load.

Introduction

A common structural element that is found in many
aerospace structures is the thin-walled curved panel with
a centrally located circular cutout. Cutouts commonly ap-
pear in curved panels as access ports, doors, or windows.
During operation, these structural elements may experi-
ence compression loads, and thus their buckling and post-
buckling behavior are important factors in determining
safe operating conditions and effective designs for these
structures.

Several studies have been presented that show that a
circular cutout in a compression—loaded composite flat

plate can have a significant effect on the buckling and

postbuckling response of the structure."3 However, sig-
nificantly fewer studies have been presented for com-
pression-loaded curved panels with a cutout. More
specifically, limited results on the effects of a circular
cutout on the buckling response of compression-loaded
aluminum curved panels are presented in Ref. 4 and lim-
ited results on the effects of rectangular cutouts and lam-
inate stacking sequence on the buckling behavior of
compression-loaded curved composite panels are pre-
sented in Refs. 5 through 8. In Ref. 4 it has been shown
that circular cutout size greatly affects the buckling char-
acteristics of compression-loaded curved isotropic pan-
els. In particular, the results indicate that aluminum
panels with cutout-diameter-to-panel-width ratios d/W
ranging from 0 to 0.3 exhibit nonlinear behavior that in-
cludes a distinct buckling event with an unstable post-
buckling response while panels with values of d/W
ranging from 0.4 to 0.6 exhibit a stable monotonically in-
creasing nonlinear load-shortening response. These re-
sults also indicate that as the value of d/W increases, the
magnitude of the nonlinear prebuckling out-of—plane de-
formations increases, which results in an increase in the
nonlinearity of the prebuckling load-shortening response
curve.