The sequence of damage in biaxial rotation fatigue of fibres

Abstract

A multiple splitting mode of failure of fibres, commonly found in textiles in use, can be simulated in the laboratory by a biaxial rotation fatigue test. The paper reports on the development of damage in polyester (PET) and nylon fibres with increasing numbers of cycles, as shown by loss of strength and by crack development observed in SEM or direct observations. Initiation regions, with no loss of strength and crack development regions, with a linear loss of strength, are found. In a coarse polyester fibre, there were two such regions, before final failure, and the damage split into separate zones, both along and across the fibre. In finer fibres, with lower bending strain, there was only one sequence and no observable separation of zones of damage. The effects are discussed in terms of the various stresses imposed on the fibre during the test.