Mechanism of mechanical strengths is discussed for corrugated fiberboards of single face, single wall and double wall. The strength under the tensile load is discussed by the experimental results of the tensile deformation. Their strengths under the surface compression and the uniform bending made from the applied moment of the axis along the machine direction are discussed by elastic theory. Different mechanism of the strength is denoted for the deifference of the fiberboard.
From the mechanism, the argument of the design for their fiberboards is performed on obtained effective results. And the determination of the reasonable shape for their fiberboards is studied from the obtained stress behavior.