Energies 2021 , 14 , 3203
4of 16
crushing. The results obtained in the SST laboratory tests are valid also for highly crushed or broken samples.
( a )
( b )
( c )
Figure 2. The edge crush test: ( a ) corrugated board testing device; ( b ) loaded sample; ( c ) de- formed sample.
( a )
( b )
( c )
Figure 3. The shear stiffness testing: ( a ) cardboard testing device; ( b ) loaded sample; ( c ) de- formed sample. In the torsional stiffness (TST) measurement, a twisting of a 25 × 150 mm sample by a few degrees in both directions is conducted, see Figure 4. The results obtained are valid even for highly crushed or broken samples. Therefore, the TST parameter has a high sensitivity to crushing of the corrugated board sample. Only the linear part of a diagram (i.e., the angle of rotation vs bending moment) is used to determine the sample torsional stiffness. The reliable measurements are assured by: (1) a stable method of holding the sample, (2) a static method of measuring the angle of rotation and torque and (3) a relatively large width of the sample, thanks to which the sample behaves as a homogenized material.
( a )
( b )
( c )
Figure 4. The torsional stiffness test: ( a ) cardboard testing device; ( b ) loaded sample; ( c ) de- formed sample. The crushing device (CRS) is used to assess the impact of converting processes such as laminating, stamping, creasing or printing on the quality and load-bearing capacity of the corrugated board, see Figure 5. In this research, a fully controlled manner of crushing cardboard in the range from 10% to 70% was precisely obtained by using the CRS laboratory device (fematsystems.pl/services/crs [33]), which assured the crushing accuracy of ± 10 μ m. In Figures 1–5, the devices for different testing methods of corrugated cardboards are presented. Furthermore, the loading scheme of the sample (Figure 5b), as well as the
Made with FlippingBook Online document maker