The md or lateral shear stiffness can be thought of as indicating the ability of the corrugated board to resist machine direction sliding of the two liners with respect to each other (see Figure 1). This property is important in managing bulging in loaded corrugated boxes and poor shear performance can often be caused by loss of integrity of the combined board medium due to crushing and damage during manufacture.

The shear stiffness is affected not only by the slenderness of the medium compared to the flute height, but also the level of damage sustained during manufacture and conversion. Commonly, this damage is due to crushing from misaligned elements in the corrugating and conversion processes.

Reported work has shown that diminishing board core shear stiffness can lower the box strength by up to 40%. Even quite moderate crushing will lower box potential by 10% or so. The real impact of induced manufacturing medium damage is seen when one explores the impact of corrugated performance loss on field performance.

Field performance is generally viewed as the fitness of the packaging to contain, ship and support the product from packing to its ultimate destination – either in domestic logistics chains or the more severe export chain.

Often boxes are required to withstand severe environmental conditions during their time of service and this can take the form of changing temperatures, humidities, vibration and shock events. Depending upon the application, the time that a box must support loads and the load itself when boxes are stacked on pallets may vary. It is the effect of medium damage on stacking survival time that is most disturbing.