ABSTRACT
Ceramics work better in compression than in tension. A number of defects are incorporated into them during their manufacture from powders. These defects play an important role in decreasing their tensile properties and in causing brittleness. Plastic deformation is almost negligible because dislocations cannot move easily. Fracture takes place mostly along grain boundaries. A comparison of the tensile properties of three classes of materials is shown in Figure 15.1. For ceramic, its modulus of elasticity and fracture strength are the highest; it does not have plastic deformation; and it is the least tough. Metal possesses the highest toughness, an intermediate modulus of elasticity, and shows plastic deformation. Elastomers have the highest ductility, intermediate toughness, and the least strength.
