Torsional fatigue and the initiation mechanism of pilling [of fibers on the surface of a fabric]

Torsional fatigue studies in polyester fibers have revealed that the fracture morphology of ruptured fiber surfaces is influenced by the level of torsional strain amplitude. At relatively high strain ampli tude the mechanism of fracture seems to be governed by the propagation of a single large crack. However, at low strain amplitudes, the fibers exhibit a slow and gradual breakdown of structure, starting with the surface layers. The surface morphology and the fracture phenomenon observed in the later case essentially resemble what happens in the formation of pills from polyester fibers in garments.