Fatigue failure in technical polyamide 66 fibers

The fatigue behavior of technical polyamide 66 fibers is studied using two samples with different diameters. First, the structural and viscoelastic pr operties are characterized, and then loading criteria for fatigue failure a re identified. The fatigue fracture morphology revealed by scanning electro n microscopy is quite different from simple tensile fracture morphology. Ma ny theories have been advanced to explain the fatigue failure phenomenon. T his work shows that fatigue failure is initiated at the surface of the fibe r and not in the interior, as some using the Prevorsek model have suggested . On the other hand, fatigue failure is independent of fiber geometry, and a relaxation thermal treatment considerably reduces fatigue.