High fiber volume fraction metal matrix composites cast under bi- dimensional compression

Abstract

Metal matrix composites (MMCs) are currently receiving much interest in the materials community. These materials may be engineered to specific design needs by varying the reinforcement material and morphology. The primary advantage of these materials is their high strength and stiffness relative to their density. This project focuses on a class of metal matrix composites which derive their strength and stiffness from continuous unidirectional fiber reinforcement. The technique of bi-dimensional compression was used to fabricate metal matrix composites of this type. The advantage of the technique is its unique bi-dimensional stress field which creates a uniform fiber array and volume fractions approaching the theoretical maximum for rigid fibers. The composites produced in this study are characterized by optical and electron microscopy which allows qualitative observation of the fiber distribution, matrix infiltration, void morphology and fiber/matrix interface. Quantitative measures of the quality of the specimens are obtained from fiber volume fraction, density and modulus measurements. The bulk of the specimens were fabricated in the form of parallelepipeds, which is the shape created by the interlocking dies of the bi-dimensional compression device. However, the flexibility and versatility of the technique were demonstrated by the production of circular cylinders and tubes which were reinforced in the longitudinal direction.