Flat crush resistance serves to define the corrugated cardboard resistance. The level of the flat crush resistance depends on the flute material and the type of the flute.
Walls simply retain the shape and do not influence the crash resistance. Round samples, 90mm in diameter, are cut out of the cardboard, and then crushed between two crushing plates.
The pressure necessary to deform the flute is then measured. The results are expressed in kPa.
The equivalent of the FCT test in the case of measuring the flute resistance to flat crush is CMT test.