Elastic Strength of Corrugated Fiberboard under the Uniform Bending about the Moment Axis in the Machine Direction

V-DWCF of Asymmetric Strength for Thickness

Abstract

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 KL₁, lower KL₂ and middle KL₀) or semi-chemical corrugated medium (SCP medium : upper CM₁ and lower CM₂). Obtained results are as follows ;
(1) Vertical distance h₀ from the outer surface of KL₂ 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 h₁ for CM₁. It decreases initially and then approaches constant gradually with the increase of wavelength L₁ for CM₁.
(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 CM₁, CM₂, KL₁, KL₂ and KL₀.
(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 L₁. It increases initially, attains maximum and then decreases gradually with h₁. 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 h₁.
(4) σ_k1max decreases remarkably with the increase of T_s1, T_k1 and T_k0, but increases with the increase of L₁ and E_k1. It also increases initially, attains maximum and decreases gradually with the increase of h₁.
While σ_k2max decreases with the increase of T_s1 and T_k0, and increases with the increase of L₁. But it increases initially, attains maximum and then decreases gradually with the increase of h₁, E_k1 and T_k1.