Single wall corrugated fiberboard is specified on one line
and double wall is specified on two lines.
The components of double wall board code 275BC are specified from left to right and from top to bottom, again in the same order they are combined on the corrugator. The two flute sizes are also specified in the order of combining. Each flute size is for the single face and corrugating medium combination on the same line. Only one double back component exits, regardless of single, double, or triple wall construction.
The orientation of asymmetric construction has little effect on combined board properties. The strength and stiffness of material 275BC is shown to be identical to the strength and stiffness of material 275CB, although box strength from these materials differed in Example 1.1. However, the effective stress-strain properties of these materials in files PLATEC.PRN and PLATEM.PRN are a function of asymmetry. Thus, combined board properties should not be relied on solely at a predictor of box strength.
Board codes 90%BC and 90%CB are the same as 275BC and 275CB, respectively, except for the substitution of material 90% for the double back component. It will be shown in an upcoming example how material 90% was specified to characterize paper subject to 73o F and 90% RH.