MICROFRACTURE MECHANISMS OF FIBER-REINFORCED ALUMINUM COMPOSITES

The microfracture mechanisms of aluminium matrix composites reinforced with SiC-based fibres are examined such that the events of crack initiation and propagation are recorded in situ in a scanning electron microscope. The specimens are loaded by an electronically controlled device for which four different loading conditions are considered: longitudinal tension, longitudinal compression, transverse tension and transverse compression. Under longitudinal tension cracks initiated at an interface layer between the fibre and matrix, while longitudinal compression gave way to debonding of the fibre near the specimen edge, leading to microbuckling of the fibres and further debonding. Initial microcracks near the specimen edge as a result of machining tend to enhance fibre splitting in a zigzag pattern when stretched in the transverse direction. Transverse compression led to cracking of the matrix, where severe distortion was observed. Failure caused by fibre debonding and crushing appears to coincide with the plane of maximum shear.