Interlaminar Shear

Board Converting

Creasing operations generate severe localized deformation to facilitate clean folding along pre-defined lines. For optimal box-making, the paperboard must allow a controlled failure under interlaminar shear during the scoring step. This localized delamination creates an internal hinge that reduces the force needed to fold the carton.

If the bonding is too high, the surface plies will crack or rupture during folding, which exposes the grey board beneath and ruins the visual appeal of the printed carton.

Testing Standard

Standardized mechanical trials evaluate the ply-bond strength of paperboard under controlled rates of displacement. The humbinger or scott internal bond test applies a dynamic impact to measure the resistance to interlaminar shear. This procedure uses a weighted pendulum to strike a metal angle glued to the board sample, calculating the energy absorbed during the rupture.

Consistent test values ensure that the board will withstand the mechanical stresses of high-speed filling lines.