THE FLEX FATIGUE OF POLYAMIDE AND POLYESTER FIBERS .2. THE DEVELOPMENT OF DAMAGE UNDER STANDARD CONDITIONS

Polyamide and polyester fibres have been subjected to flex fatigue by pulling to and fro over a pin, in order to investigate the alternative damage modes, namely cracks along kink-bands due to compression, and axial splitting due to shear stresses. Initial studies determined the conditions that were sufficiently severe to give a short enough test t ime but not so severe that abrasion on the pin was dominant. Fibres we re then cycled for varying periods, the damage viewed in a scanning el ectron microscope, and the change in tensile properties, including res idual strength, determined.