Especially with new or further developed glass fibres lining tubes, an extremely strong increase in the flexural modulus can be observed in order to minimize the wall thickness of the tube.

According to worksheet DWA-A 143-2, the static proofs must always be carried out for two different types of failure. Liners can break, especially if the flexural stress is too high (rupture failure). To minimise the wall thickness, a sufficiently high flexural strength of the liner wall is therefore aimed for on the material side.