Volume 14, Issue 3, 2005

DAMAGE MODELLING AND SIMULATION OF COMPOSITE MATERIALS USING ULTRASONIC MEASUREMENTS

A. Paipetis^1,2, Y. Z. Pappas^1,3, D.E. Vlachos¹ and V. Kostopoulos<sup>1

1</sup>Applied Mechanics Laboratory, Dept of Mechanical & Aeronautical Engineering, University of Patras
²Marine Materials Technology Dept, Hellenic Naval Academy
³Moody S.A., Member of Moody International Group of Companies, Athens

(Received 12/04; accepted 6/05 )

ABSTRACT
The monitoring of the elastic properties of Al2O3/Al2O3 composites during the exposure at high temperature environment that simulates the working conditions of a gas turbine has been performed non-destructively using ultrasonics. The applied methodology is based on velocity measurements of the elastic waves that propagate in an orthotropic medium. These were estimated experimentally using a custom pulser-receiver setup which allows control of the angle of the incident pulse on the sample, while the latter is immersed in a water bath. The derivation of the elastic constants in order to reproduce the stiffness matrix of the composite is an inverse wave propagation problem described by the Christoffel equation. The damage initiation and propagation as depicted by the deterioration of the moduli of the material was described using deterministic and stochastic approaches. Finally, the damage accumulation process was simulated as a Markov process.