ISO 11093-8:2017 specifies a method for the determination of the flexural modulus by using experimentally measured natural frequencies in the free-free mode of transverse vibration of cylindrical paper and board cores, which meet the following criteria:
- internal diameter:
50 mm to 350 mm;
- minimum wall thickness:
0,02 × internal diameter or not less than 2,0 mm;
- minimum length of core:
8 × internal diameter.
NOTE For the determination of the flexural modulus by the three-point method, see ISO 11093‑7.