Analysis of the bending stress is performed for double wall corrugated fiberboard (DWFC) with asymmetrical strength distribution along the direction of thickness of the kraft-liner (KL). Relations are investigated between maximum absolute stresses of elements for DWCF (σ
s1max, σ
s2max, σ
k1max, σ
k2max and σ
k0max) and shapes for upper KL (Upper KL
1, lower KL
2 and middle KL
0) or semi-chemical corrugated medium (SCP medium : upper CM
1 and lower CM
2). Obtained results are as follows ;
(1) Vertical distance h
0 from the outer surface of KL
2 to the neutral surface of DWFC increases with increasing modulus E
k1 of longitudinal elasticity. thickness T
K1 for KL, and thickness T
s1 and waveheight h
1 for CM
1. It decreases initially and then approaches constant gradually with the increase of wavelength L
1 for CM
1.
(2) Stresses in KL and SCP medium are proportional to the distance from the neutral surface to the point interested in. σ
s1max, σ
s2max, σ
k1max, σ
k2max and σ
k0max occur at the outermost positions, that is, on the outermost surfaces for CM
1, CM
2, KL
1, KL
2 and KL
0.
(3) σ
s1max decreases remarkably or slowly with the increase of T
s1, E
k1, T
k1, and thickness T
k0 for K
L0 but increases with the increase of L
1. It increases initially, attains maximum and then decreases gradually with h
1. σ
s2max increases initially, attains maximum and then decreases gradually with of E
k1, T
k1 and T
k0 It decreases with the increase of T
s1 and h
1.
(4) σ
k1max decreases remarkably with the increase of T
s1, T
k1 and T
k0, but increases with the increase of L
1 and E
k1. It also increases initially, attains maximum and decreases gradually with the increase of h
1.
While σ
k2max decreases with the increase of T
s1 and T
k0, and increases with the increase of L
1. But it increases initially, attains maximum and then decreases gradually with the increase of h
1, E
k1 and T
k1.
View full abstract