Dynamic Strain Rate Modeling for Multi Ply Boxboard under Rapid Compression
Dynamic strain rate modeling predicts multi-ply boxboard Z-direction compression and interlayer shear collapse during high-speed converting and package drops.
Dynamic Modulus
Elastic Response
Measuring the ratio of stress to strain under vibratory conditions defines the stiffness of a material subjected to rapid, cyclical loads. The dynamic modulus characterizes how a polymer film or coated paperboard behaves when it experiences rapid compression or stretching. This property determines how well a material can absorb vibrations without permanent deformation.
Frequency Dependence
Cellulose fibres and synthetic binders exhibit viscoelastic properties that change depending on the rate of the applied forces. The dynamic modulus increases at higher frequencies because the polymer chains have less time to rearrange and relieve the stress. This means that a carton board will behave as a much stiffer material when dropped than when sitting statically on a store shelf.
Testing this property at various frequencies allows designers to predict the performance of the packaging during transit and storage.
Converting Behavior
Operating high-speed printing presses and folder-gluers exposes the web to intense, repetitive tension cycles. The dynamic modulus determines the tension stability of the paperboard web as it passes through the printing rollers and folding guides. If this value is too low, the web will stretch excessively, which leads to poor color register and inaccurate creases.
Managing this viscoelastic stiffness ensures that the board runs smoothly through the machinery without tearing.