Ring crush of paperboard (flexible beam method)

The ring crush test correlates with edgewise compression strength of paperboard (1).

This method is intended for paperboard between 0.28 mm (0.011 in.) and 0.51 mm (0.020 in.) thick. It may be used with less reliability for paperboard as thin as 0.18 mm (0.007 in.), and as thick as 0.76 mm (0.030 in.). The short span compression test, TAPPI T 826 “Short Span Compressive Strength of Paperboard,” measures edgewise compressive strength over a broader range of thickness.

Ring crush is also measured in TAPPI T 822 “Ring Crush of Paperboard (Rigid Support Method),” which uses a rigid platen compression machine instead of the flexing beam of this method. T 822 has a tighter precision.