Rotating-bending fatigue and torsional fatigue tests of the injection moulded short carbon-fiber reinforced polyamide 6.6 were carried out to investigate the fatigue characteristics. The fatigue mechanism in the composites was clarified through successive surface observations using the replica method. Moreover, the mechanism of the torsional fatigue was compared with that of the rotating-bending fatigue. The fatigue cracks in both fatigue tests are nucleated along the fibers aligned in the direction of the maximum principal stress. In the case of the rotating-bending fatigue test, the fatigue crack propagates at right angles to the direction of the principal stress. On the other hand, in the case of torsional fatigue, the cracks nucleated along the fibers cannot propagate under the low stress amplitude. However, the fatigue cracks nucleated from the fibers which are aligned in the direction of the principal shear stress can propagate, and lead to the final fracture.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering