Dynamic Fracture Mechanics of Multi Layer Paperboard Creasing under Rapid Shear Loading
Rapid shear creasing requires tailored interply delamination toughness to prevent liner fracturing while reducing folding torque on high-speed lines.
Dynamic Shear Loading
Stress Characteristic
Structural performance of shipping containers depends on how well the intermediate paperboard layers resist rapid lateral forces. When packages are stacked or transported, dynamic shear loading represents the sliding force exerted parallel to the surface of the paperboard. This mechanical stress occurs during transit vibrations and sudden forklift maneuvers, threatening the integrity of the fluting.
Standard board grades must possess sufficient internal bond strength to withstand these forces without delaminating.
Load Simulation
Laboratory instruments evaluate this resistance by applying rapid oscillating forces to the material. Technicians mount the test specimen between parallel metal plates that move in opposite directions at a specified frequency. This arrangement creates a high-frequency shearing motion that mimics the actual acceleration of a heavy freight vehicle.
The testing software records the peak force and the displacement until structural failure is detected. Measuring the resulting load curve allows engineers to predict how the packaging will perform under rough handling. It also helps determine the fatigue limits of the adhesive bonds.
Failure Mechanism
Material collapse occurs when the internal fibre network can no longer transfer the stress. Under repeated displacement, the fibres within the paperboard begin to separate from the synthetic binders. This micro-cracking propagates along the neutral axis of the board, leading to complete structural failure.
Understanding this degradation path helps mills optimize starch application and refining levels.