Fracture toughness tests were performed on Al₂O₃/Nb sandwich specimens using chevron-notched bending bars. These tests allow the independent determination of the fracture toughness K_c at a defined crack velocity and the total work of fracture J_c. The J_c values are much greater than the data for the energy release rate G_c following from K_c. The fracture surfaces were studied by optical and scanning electron microscopy. The results are discussed in terms of the fracture toughness of cleavage in the Al₂O₃ and severe plastic deformation in the Nb sheet.