Stiffness tester

STIFFNESS TESTER

Purpose
To determine the resistance of a paper material to a bending stress-measured as bending moment
This instrument is used to determine the flexural resistance of paper or paperboard, the stiffness of fibrous material, the limpness of flabbiness of paper and the softness of tissue.
For the purpose of this method the term used are defined as follow :
Rigidity(its property of resisting an applied bending force, its flexural resistance).
Rigidity factor(a measure of this rigidity of this structure of this sheet proportional to modulus of elasticity). Stiffness(the ability to support its own weight).Softness(the feeling of softness when a sheet is cramped).

Principle
Two different principles are commonly applied in the industry to measure the bending stiffness
Beam method. For a rigidly clamped paper strip, the deflection caused by a defined perpendicular load on the paper surface is determined.
Resonance stiffness test method
The resonance stiffness tester vibrates one end of a clamped paper strip at a constant frequency.
The test span is varied until the vibration amplitude reaches a maximum. The test span at the point

How to use
Prepare paper sample with measuring size 70mm x 50mm or more
Open up the cover tester to make it easier when sample put in.
Put in the sample between roll with vertical side and then close the cover back.
If the sample down to right, move the switch to right, then run motor until the sample down back to the left and then stop.(watch the needle, to see value degree )
If value degree of the sample measured are same right and left more than 90º, Short cut the sample. On the other hand if less length up the sample.
Repeated test again until get an amount degree right side and left side sample are = 90º
Measures cm length of sample with scale

Report count

The rigidity, rigidity factor, stiffness, or softness in such direction are calculated as follow :
Rigidity = L³ W/10.000
Rigidity factor = L³ W /100 T³
Stiffness = L³ /100
Stiffness = (106 l log (t +1))/ L³W

Where :
L = Average critical length (cm)
W = Basis weight (g/m²)
T = Thickness (mil)
t = basis thickness of a single sheet
of creped paper (mil)