Viscoelastic Creep Compliance and Interfacial Fracture Energy in Paperboard Laminates
Creep compliance dictates long-term carton deformation, while interfacial fracture energy governs delamination under score bending and pallet loads.
Burger Four Element Model
Viscoelastic Representation
Viscoelastic models describe the time-dependent deformation and recovery of polymers and paperboard fibers under mechanical stress. The burger four element model combines Maxwell and Kelvin-Voigt elements in series to represent both instantaneous elasticity and delayed viscoelastic behavior. This mathematical framework divides the strain into three distinct components representing elastic spring action, delayed elastic recovery, and viscous flow.
Creep Analysis
Mechanical stress applied to paperboard triggers a continuous deformation that accumulates over time. During this phase, the Maxwell spring responds instantly, followed by the gradual extension of the Kelvin-Voigt parallel assembly, while the Maxwell dashpot accounts for permanent deformation. The rate of this deformation depends on the viscosity of the fluid components and the stiffness of the elastic springs.
These values vary with temperature and humidity, which alter the intermolecular forces within the cellulose fiber network. Engineers use these measurements to predict how corrugated boxes will perform under long-term stacking loads in warehouses.
Recovery Phase
Removal of the external load initiates a partial restoration of the original dimensions of the material. The Kelvin-Voigt spring pulls the dashpot back to recover delayed elasticity, but the Maxwell dashpot remains extended to leave a permanent set. This residual deformation limits the reuse of the material in high-precision packaging assemblies.