The combination of superior properties and relative ease of manufacture has made metal matrix composites candidate materials for the weight-critical, damage-tolerant, and high stiffness structural applications. In this paper, the fatigue crack growth and fracture resistance obtained from single-edge notch bend specimens of the 2124 aluminum alloy reinforced with 20 wt% discontinuous silicon carbide whiskers is presented. The testing and data analyses were conducted in accordance with the ASTM standards initially designed for testing monolithic metallic materials. The suitability of these standards for testing composites is evaluated. The mechanisms of the fatigue crack propagation and stable crack growth under monotonic loading are also characterized.

The plane strain fracture toughness values and the crack growth resistance curves were very consistent among specimens of the same size, but systematic differences were measured between the properties obtained from specimens of different sizes. On the other hand, the fatigue crack growth behavior correlated uniquely with ΔK irrespective of the specimen size.

Microstructural characterization of tested specimens suggested complicated damage mechanisms accompanying the fatigue and fracture of this composite. Features, such as whisker bridging, whisker pullout, crack deflection influenced by the interfaces and whisker fracture, were observed on the fracture surfaces. These results are described and discussed in-depth in this paper.