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PARAMETRIC STUDY OF SANDWICH PANEL BUCKLING IN COMPOSITE WIND TURBINE BLADES
Shicong Miao, Steven Donaldson, and Elias Toubia
Figure 4. Flat model FEA result compare with the closed form solution
RESULTS AND DISCUSSION
Critical Buckling Load Nx*10 9
(N/m)
FEA compare with closed form solution
1200
1100
1000
900
800
700
600
500
The local buckling phenomenon, such as core shear crimping and skin
wrinkling, are discussed in references (Eringen, 1952, Vinson, 1999).
The core thickness and shear modulus must be adequate to prevent the
panel from buckling or failing under end compression loads. The
compressive modulus of the facing skin and the core compression
strength must both be high enough to prevent a skin wrinkling failure.
Since the anayzed skin material is sufficently stiff, local skin failure
was not taken into consideration herein (Toubia, 2008). Each of the
curves in the subsequent plots were created from five or six individual
calculation points. Since no dramatic shape variations were observed
in the results, for clarity the individual data points are not shown, but
smoothed lines are presented.
0 20 40 60 80 100 120
G 13 (MPa)
FEA S4R
ANALYTIC
AL
Flat Panel Core Thickness Study
Figure 5 shows the effects of increasing the core transverse shear
modulus (M1 through M4), increasing the number of facing layers (1
layer facing to 5), and increasing the core thickness (C 0 is the core
thickness divided by the facing thickness) on the critical buckling load,
N 1 . Figure 5 illustrates that a higher transverse shear modulus increases
critical buckling load. It is also clear that both increasing the number of
facing layers, as well as increasing the core thickness lead to increases
in the critical buckling load. Note that while increasing the thickness of
the core, the critical buckling loads increase faster in the cases with
higher transverse core shear modulus. Also, for increased core
thickness, a higher number of layer facing results in rapid increases in
critical buckling load. Figure 6 depicts similar trends for the laminate
critical strain values: transverse shear modulus of the core, core
thickness, and number of facing layers are the dominant aspects in
sandwich panel buckling resistance.
Figure 5. Critical buckling load versus normalized core thickness C 0 for all five facing layers and all four core materials. Flat-section. 1m width
sandwich panel.
Critical Buckling Load N 1 *10 5 (N/m)
45
40
35
30
25
20
15
10
5
0
1 3 5 7 9 11 13 15
Normalized core thickness C 0
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