Interlaminar Shear Stress

Adhesive Mechanics

Starch-based adhesives applied between linerboard and medium must penetrate the paper matrix to resist sliding forces generated during folding operations. Shear resistance depends directly on fiber density and regional moisture content established at the wet end of the papermaking machine. Low grammage substrates deployed in folding carton manufacturing require precise adhesive deposition rates to avoid excess water absorption that degrades ply adhesion.

Mill operators adjust refining intensity to increase fiber-to-fiber bonding surface areas, which directly elevates the force required to slide adjacent plies past one another.

Failure Modes

Ply separation occurs when bending moments exceed the internal adhesive capacity of composite paperboard structures. Converting facilities monitor this mechanical limit during box erection tests to eliminate carton collapse under compressive warehousing loads. Laminated packaging materials subjected to rapid thermal drying experience localized bond degradation because steam pressure within the sheet fractures internal fiber bridges.

Substrate thickness variations across a jumbo roll create uneven nip pressure in the press section, leading to localized weak spots where delamination initiates under multi-axial stress states.