ICIFUAS 11
Eleventh International Conference on Internal Friction and Ultrasonic Attenuation in Solids

J. Phys. IV France 06 (1996) C8-747-C8-750
DOI: 10.1051/jp4:19968162

The Internal Damping of Al-Al₂O₃ (f) Composites During Thermal Cycling : the Effect of Fibre Content and Matrix Strength

S.E. Urreta¹, R. Schaller², E. Carreño-Morelli^{2, 3} and L. Gabella<sup>2

1</sup>  Facultad de Matemática, Astronomía Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina
²  Ecole Polytechnique Fédérale de Lausanne, Institut de Génie Atomique, PHB-Ecublens, 1015 Lausanne, Switzerland
³  Centro Atómico Bariloche and Institute Balseiro, Comisión Nacional de Energía Atómica and Universidad Nacional de Cuyo, 8400 Bariloche (Argentina)

Abstract
A simple model is proposed to describe the observed effect of the volume fraction of fibres on the internal friction, elastic modulus and deformation at zero applied stress during the cooling portion of a thermal cycle between 450 K and 100 K. The sample is considered as composed by three phases, each one showing different intrinsic damping: the reinforcing fibre, the aluminium matrix far from the fibre and the zone around the fibre, close to the matrix-fibre interface, called the plastic zone. It is assumed that the main contribution to the internal friction arises in these plastic zones, which grow during cooling in a non strain hardening matrix. A uniform dislocation density in the zone is considered. The internal damping of the whole sample is predicted, as a function of fibre content, for the limit case of uniform strain. The model predicts satisfactorily the characteristic temperatures defined in the elastic modulus curve if they are identified as the temperatures for the beginning of growth of the plastic zone, and the temperature for overlapping of fully developed zones, respectively.

© EDP Sciences 1996