Complete determination of elastic moduli of interpenetrating metal/ceramic composites using ultrasonic techniques and micromechanical modelling

The complete stiffness matrices of several metal/ceramic composites were analysed using the complementary ultrasonic spectroscopic techniques ultrasound phase spectroscopy (UPS) and resonant ultrasound spectroscopy (RUS). Three different aluminum/alumina composites having complex interpenetrating architectures were studied: a composite based on freeze-cast ceramic preform, a composite based on open porous ceramic preform obtained by pyrolysis of cellulose fibres, and a composite based on discontinuous fibre preform. Six of the nine independent elastic constants describing orthotropic elastic anisotropy were pre-determined by ultrasound phase spectroscopy and used as initial guess input for resonant ultrasound spectroscopy analysis, making the final results of all nine elastic constants more reliable. In all cases, consistent and reproducible results are obtained. Finally the experimental results were compared with effective elastic constants calculated using micromechanical modelling and a good correspondence between both is obtained.