FRACTURE AND FATIGUE-CRACK GROWTH-BEHAVIOR OF SICW 2124A1 COMPOSITE/

The combination of superior properties and relative ease of manufactur e 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 obtai ned from single-edge notch bend specimens of the 2124 aluminum alloy r einforced with 20 wt% discontinuous silicon carbide whiskers is presen ted. The testing and data analyses were conducted in accordance with t he ASTM standards initially designed for testing monolithic metallic m aterials. 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 plan e strain fracture toughness values and the crack growth resistance cur ves were very consistent among specimens of the same size, but systema tic differences were measured between the properties obtained from spe cimens of different sizes. On the other hand, the fatigue crack growth behavior correlated uniquely with Delta K irrespective of the specime n size. Microstructural characterization of tested specimens suggested complicated damage mechanisms accompanying the fatigue and fracture o f this composite. Features, such as whisker bridging, whisker pullout, crack deflection influenced by the interfaces and whisker fracture, w ere observed on the fracture surfaces. These results are described and discussed in-depth in this paper.