Lightweight Electric/Hybrid Vehicle Design

206 Lightweight Electric/Hybrid Vehicle Design
S
Core
1/3 2/3 0.63E Ec
f
where E is the elastic modulus for face and core.
For column buckling of the panel, the parameters of panel length and edge support must also be
considered – together with thicknesses of face and core plus the bending stiffness of the combination.
To calculate sandwich panel bending stiffness it is generally assumed that shear stress is
uniformly distributed across the core. Central deflection for a uniformly loaded (w per unit length)
sandwich panel of moderate width, simply supported at its ends, is, for dimensions seen at (a),
given by:
(5wl 4 /384E f I) + (wl 2 /8G c A)
where l is the length between supports, A is the core cross-section area, I the section second
moment of area and G c the shear modulus of the core material. To allow simply supported panels
to be designed without resort to complex calculation, correction factors shown at (b) have been
P
P b
t f tc
S
l
Faces
1.0
C2 p.lb/in
0.5
C1 l2 l2 0
1.0
≤ l1 2.0
l1 3.0
2
Ks 10
0.40 Ksp
Ksp
8
0.35
6
Ks
0.30
4
2
0.25
l1
l2
0
1.0 1.5 2.0 2.5
Stenderness ratio,
3.0 3.5
0.20
4.0
L (a)
(b)
(d)
/b
Fig. 8.4 Foam-cored sandwich panels: (a) sandwich panel parameters;
(b) correction factors; (c) failure modes; (d) K factors.
(c)
P CR W
P CR W
P CR B
P CR B
S CR
P
S CR