Theory

Program PPR converts experimental data containing paper basis weight, thickness, strength, and stiffness properties, obtained from specimens at specific basis weights, into fundamentally more general stress-strain properties for input to ECT at arbitrary basis weights. PPR corrects for instrumentation and can estimate a complete set of paper stress-strain properties when some of the experimental inputs are not obtainable.

Program ECT applies a special plate theory, developed specifically for nonlinear elastic material like paper, to determine the critical buckling strain of a plate structure and the stress in each structure element from the outputs of PPR. The solution procedure enables plates to be geometrically connected along common boundaries with only a small number of degrees-of-freedom needing to be considered. Outputs of edge crush strength and bending stiffness become inputs to BCT.

Program BCT applies an advanced box compression theory to the outputs of ECT. The predictability of box strength from paper properties starting with PPR enables more rational safety factors to be applied and opportunities to reduce costs to be quantified.