Mechanics of Cellulosic Wall Collapse during Micro Scale Tooling
Micro-scale tooling forces hollow cellulosic cell walls past transverse yield, where apex radii under thirty micrometers balance wall densification against fiber shear.
Shear Failure
Material Rupture
Structural collapse occurs when the internal layers of a material slide past one another due to forces acting parallel to the surface. The condition of shear failure is observed in corrugated board when the adhesive bond between the fluting and the liner yields under a lateral load. This separation destroys the rigidity of the board and causes the box to buckle or lean.
Bond Evaluation
Laboratory evaluations measure the force required to induce this type of breakage in a standardized sample. In a pin adhesion test, the strength of the bond is challenged to see if the glue line or the paper fibers themselves will experience shear failure first. A clean break in the adhesive suggests that the glue application was insufficient or that the temperature during the corrugating process was too low.
If the failure happens within the paper, the fiber strength is the limiting factor for the performance of the packaging.
Load Mode
Combined loads in a stacking environment often lead to complex deformations that involve both compression and sliding. When a shipping container is subjected to horizontal impacts or vibrations, shear failure can occur along the score lines where the material is already weakened.