NUMERICAL-SIMULATION OF MICROSTRUCTURE AND STRENGTH PREDICTION FOR SHORT-FIBER-REINFORCED METAL-MATRIX COMPOSITES

In this paper, the microstructure of a short-fiber-reinforced metal-ma trix composite (MMC) material is simulated by computer. The real distr ibution of short fibers in an Al-Mg5.5 metal-matrix composite is obtai ned from experimental observation, and the length of 'Saffil' short Al 2O3 fiber in the metal matrix is also obtained. It is found that the d istribution of short fibers is approximately 2-D random distribution. Numerical microstructural pictures are compared with experimental SEM photographs. In the simulation, the fiber orientation, fiber diameter, fiber length and fiber location are considered. The microstructural e ffects of average fiber length and diameter and their distributions on the macroscopic strength of metal-matrix composite materials are anal yzed for different fiber volume fractions. The short-fiber orientation coefficient, xi(a), short-fiber diameter coefficient, xi(d), and shor t-fiber length coefficient, xi(l), are obtained from microstructural d istributions of fibres in MMC materials. Considering these coefficient s xi(a), xi(d) and xi(l), an improved formula for the macroscopic stre ngth of short-fiber-reinforced composite materials is given. The resul ts from the improved strength formula show good agreement with direct microstructural calculations and experimental values. It is found that the average lengths of short fibers in composite materials may be mar kedly shortened in the manufacturing process, which may substantially affect the strength of composite materials. (C) 1998 Published by Else vier Science Ltd. All rights reserved.