Fracture Mechanics
Numerical simulation methods predict how energy dissipates during the separation of laminated paperboard plies or glued interfaces. A cohesive zone model represents this failure process by applying traction separation laws across an artificial interface before physical debonding occurs. This mathematical approach calculates the relationship between the stress across an interface and the corresponding separation distance to determine when a joint fails.
These functions allow engineers to predict delamination within complex converting processes where standard stress analysis fails to capture the non-linear zone.
Failure Criteria
High speed die cutting and folding operations generate stress concentrations that challenge the internal bond strength of multi-ply substrates. Material performance depends on the energy required to create a new crack surface which the cohesive zone model characterizes through a specific work of fracture parameter. Conversion lines utilize this data to establish safe strain limits for adhesive application and prevent surface peeling under mechanical loads.
Laboratory testing provides the traction separation curves required for accurate modeling while accounting for variations in moisture content or board density.
Interface Dynamics
Accurate predictions of edge delamination require the integration of these models into finite element analysis software for packaging design. Simulation engineers select the appropriate shape for the traction separation function to match the measured behaviour of specific barrier coatings or adhesive layers. A triangular shape approximates the response of brittle interfaces, whereas a trapezoidal distribution better describes the behaviour of ductile glue lines that undergo plastic deformation.
Calibration involves comparing simulation outputs against standardized peel tests to ensure that the chosen model accurately captures the physical resistance of the material bond. The accuracy of the simulation depends entirely on the fidelity of the input parameters to the actual mechanical properties of the substrate.
