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Mechanical Analysis of Folding Induced Failure in Corrugated Board: A Theoretical and Experimental Comparison

The problem of failure in the facings of a corrugated board is investigated by means of a mechanical model utilizing the principles of continuum damage mechanics. To evaluate the predictive capability of the model, experiments have been conducted on in-plane isotropic single- and two-ply paper sheets manufactured in the laboratory. It is found that there is a qualitative agreement between model and experiments. The model can predict if delamination will occur before the top-ply loses its in-plane load carrying capacity due to material degradation. To circumvent delamination problems, a material with low stiffness should be used in the top-ply (as compared to the bottom-ply) and a very thin top-ply should be avoided. It is exemplified that it is possible to steer the failure mode by optimizing the degree of beating or the ply thickness. It is demonstrated that plasticity may be omitted in the analysis if one is only interested in characterizing the expected type of failure mode. An important key result is that, if the circumstances are that severe damage growth takes place in the crack-tip region, then delamination most likely occur which may be in contradiction to what is anticipated from classical theories of fracture mechanics.