Cyclic saturation and fatigue fracture of tungsten monofilament-reinforced multicrystalline copper composites

Studies on cyclic saturation and fatigue fracture behavior have been conducted on tungsten monofilament-reinforced multicrystalline copper composites. A model was proposed to link the cyclic stress–strain response of the multicrystalline composites to those of monolithic single crystals and fibers. The results calculated by the model show very good agreement with the experimental data at all applied strain amplitudes by which the composites were fatigued. The fatigue fracture mechanism of the composites highly depends on applied plastic strain amplitudes. Most cracks initiate at grain boundaries in the matrix, and propagate toward and break the fiber at low and intermediate plastic strain amplitudes. At a high plastic strain amplitude, fatigue cracks initiate at the fiber even before surface cracks become pronounced, and propagates from inside outwards at a high growth rate.