Fracture Method
A standardized test geometry consisting of a specimen with two protruding arms loaded in tension facilitates the measurement of interlaminar fracture toughness. The double cantilever beam provides a way to evaluate how well the layers of a multi-ply paperboard resist splitting. A pre-existing crack is introduced at one end of the sample between the layers.
Force is applied to pull the arms apart, driving the crack further into the material.
Energy Measurement
Data gathered from this configuration allows engineers to calculate the strain energy release rate required for delamination. During the test, the relationship between the applied load and the displacement of the arms is recorded continuously. This information reveals how the internal fibre structure absorbs energy before the bond fails.
In the context of folding cartons, a high resistance to opening in a double cantilever beam test suggests that the board will not split when the corners are glued and stressed.
Application Scope
Manufacturers use this method to optimize the starch application or refining levels in the middle plies of a sheet. It functions to distinguish between the internal bond strength and the surface pick resistance of the outer liners. Precise control of the delamination resistance ensures that the package maintains its structural stiffness while allowing for clean die-cutting operations.
