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The anisotropic elastic properties of two Aluminium Matrix Composites (AMC) were characterised using an ultrasonic method. The composite materials, fabricated by squeeze casting included aluminium matrix reinforced by alumina fibre and carbon fibre, respectively. The elastic constants were determined using an optimisation method associated to a classical ultrasonic immersion device. The methodology to recover the elastic constants consists in minimising the square deviation between calculated velocities and the experimental ones, measured under variable incidence from a computer controlled ultrasonic immersion device. The method of optimisation we use in this work is based on Levenberg–Marquard algorithm allowing a better convergence to the physical solution of the inverse problem. The elastic anisotropy of the two materials is discussed and the results are compared to experimental data taken from tensile tests and to values obtained by two models: the rule of mixture and a simplified Eshelby model.