Basic Aspects of Damage Accumulation on Monolithic Metallic and Composite Materials.

The fatigue damage accumulation in high-strength structural materials occurs predominantly nonlinearly. This is true both for the individual stages of the fatigue process in metals (total life, technical crack initiation stage, crack propagation stage) and for the fatigue behavior of the new hybrid composite material ARALL and for carbon-fiber reinforced plastics. There are various indications that, if the mechanics contributions to the damage process are eliminated, the fatigue damage progression is generally accelerated, due to the existing nonlinearities in the cumulative damage processes. This is independent of the individual microstructure of the materials. Reliable analytical methods for the consideration of the nonlinearities in the accumulation of the fatigue damage have not existed until now. However, progress regarding the development of fatigue life prediction methods may be achieved in a more effective manner if the damage processes in the different types of materials are investigated in a simultaneous manner rather than by individual studies of the different materials.