Multi-Scale Mechanical Behaviour of a Highly Porous Alumina Based Foam

This work aims to characterize mechanical properties (strength and fracture toughness) of an alumina-based ceramic foam exhibiting a pore volume fraction around 88% with a multi-scale porosity ranging from 300 to < 2 mu m with a slight interconnectivity of cells. Young's modulus determined by three different methods (resonance, ultrasonic and compression) has been estimated to approximately 4 GPa which is a remarkable value for materials exhibiting such a porous volume. Moreover, regarding solid material, a value of 380 GPa taking into account the imperfect purity of alumina and the effect of grain boundaries has been determined by indentation at nano-scale. Values predicted by Ashby-Gibson and Pabst analytical models provide reliable results concerning the significant interconnectivity of porous cells in the microstructure. Finally, compressive, bending strengths and fracture toughness are respectively close to 2 MPa, 1 MPa and 0.1 MPa m(1/2). These values are in agreement with the results obtained by some authors for alumino-silicate based foams exhibiting close compositions.