Journal of the American Ceramic Society, Vol.103, No.4, 2780-2790, 2020
Mechanical properties of illite-based ceramics with controlled porosity studied by modern in situ techniques
Deformation tests combined with modern in situ acoustic emission (AE) and digital image correlation (DIC) techniques were applied to monitor low strain rate compressive behavior of illite-based ceramics with controlled porosity (P). A strong effect of porosity on the mechanical performance was observed: Young's modulus decreased linearly from 29.4 +/- 1.1 GPa (P = 14 vol%) to 3.0 +/- 0.5 GPa (P = 55 vol%) and compressive strength decreased from 307 +/- 13.6 MPa (P = 14 vol%) to 27.7 +/- 1.0 MPa (P = 55 vol%). The AE and DIC techniques revealed a transition from brittle fracture to gradual localized crushing with increasing porosity. The AE signals possessed high-energy burst-like characteristics typical of brittle fracture and (micro)cracking. The AE data showed continuous activity from the beginning of loading, suggesting that true elasticity does not occur in this material. The combination of mechanical tests with in situ techniques, therefore, proved to be particularly effective in providing additional information on the deformation dynamics in ceramics.