Fracture toughness testing of small ceramic discs and plates

A new fracture toughness test for discs and plates is presented, which can be applied to small specimens (>5 mm diameter). A semi-elliptical surface crack is made into the centre of the top plane using a Knoop intender. Then the layer containing the plastically deformed zone is ground off and the crack is loaded in tension using the Ball-on-3-Balls test.Applied to five different ceramic materials the results gained with the new method agree well with those of standardised methods.