Bending Stiffness Testing

The bending stiffness rate of corrugated board is of major importance for determining the overall, top-to-bottom stacking strength of a finished corrugated box, as well as determining the box’s ability to resist buckling.

Bending stiffness is closely related to the thickness of the corrugated board materials making up the box as well as the quality of the inner and outer liner layers of the corrugated board. These are all factors that may change during production, thus changing the quality of the finished product. So, testing the bending stiffness rate of corrugated board, both before and after converting it into its final box shape, is usually necessary.

This packaging test measures the flexural rigidity and cross direction rigidity of corrugated boards using the four-point method.

Package testing and packaging materials testing are important parts of the research and development process. Package evaluation through packaging tests help to ensure that all corrugated board products and new package designs are created specifically to handle real-world situations.


ISO 5628

TAPPI T836: Bending Stiffness four-point method. 

This procedure specifies the method of determining the bending stiffness, also called flexural rigidity, in the machine and cross directions, of corrugated board using four-point loading. The procedure may also be used for solid boards and paperboard. The method is applicable to boards with a bending stiffness of 0.5 – 200 Nm.

ISO 5628: Paper and board – determination of bending stiffness – general principles for two-point, three-point and four-point methods.

Specifies three test methods for determining the bending stiffness of paper and paperboard. The test methods differ in the type of loading mode. For paper and paperboard in a low thickness range, the two-point bending method and the three-point bending method are suitable. For corrugated fibreboard and board with a higher thickness, the four-point bending method is recommended. The measurement conditions are defined in such a way that the test piece is not subjected to any significant permanent deformation during the test, nor is the range of validity of the equations for calculating the bending stiffness exceeded.


L&W 4-Point Bending
Stiffness Tester

Bending Length: 2″- 12″ (50mm – 300mm)
Dead Weights: 0.044lb – 2.25lb (20g – 1,020g)
Maximum Thickness: 0.6″ (16mm)