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An experimental study of the R-curve behaviour of an Alumina ceramic by in-situ SEM has yielded detailed information on the extent of the R-curve in this material as well as on the actual physical mechanisms responsible for the toughness increase. These have been identified as both ligamentary bridging due to crack bifurcation and bridging by wedged grains between the crack faces which dissipates energy by friction. Simple modelling calculations show that these mechanisms can account for the 75% increase in toughness observed using the double torsion technique. Further, the feasibility of Plaster of paris as a model ceramic material for damage mechanics investigations has been examined and extensive mechanical property characterization has been carried out. Keywords: Ceramics; Alumina; Fracture; R-curve; Scanning electron microscopy; In-situ observations; Damage mechanics; Uniaxial and Hydrostatic compression; Plaster of paris.

An experimental study of the R-curve behaviour of an Alumina ceramic by in-situ SEM has yielded detailed information on the extent of the R-curve in this material as well as on the actual physical mechanisms responsible for the toughness increase. These have been identified as both ligamentary bridging due to crack bifurcation and bridging by wedged grains between the crack faces which dissipates energy by friction. Simple modelling calculations show that these mechanisms can account for the 75% increase in toughness observed using the double torsion technique. Further, the feasibility of Plaster of paris as a model ceramic material for damage mechanics investigations has been examined and extensive mechanical property characterization has been carried out. Keywords: Ceramics; Alumina; Fracture; R-curve; Scanning electron microscopy; In-situ observations; Damage mechanics; Uniaxial and Hydrostatic compression; Plaster of paris.