Moderators: Ronald Kerans, Wright-Patterson; Rowland Cannon, Lawrence Berkeley Lab

Debators: Tony Evans, Princeton; Edwin R. Fuller, NIST, Brian Cox, Rcokwell, and Peter Gumbsch

• Background
• Debate Format
• Electronic Questions Forum (add your own questions for the debators)

Background
As a scientific and technical community, we have made great progress in the development of tough ceramics. We now understand the basic principles of how microstructural mechanisms give rise to toughness and, in fact, select and design structural materials on the basis of their microstructure. Our understanding derives from fracture mechanics.

Although we employ fracture mechanics models for prediction, the models only remotely, if at all, resemble the microstructures of real materials.

For instance, this is how cracks are described in fracture mechanics textbooks:

And this is kind of microstructure that we apply such calculations to:

Two phase, anisotropic, highly irregular microstructures, lots of defects, etc.

• Why should such simple models give us any insight at all into the behavior of structural ceramics?
• Is a more realistic model possible? If we had a realistic model, would it be more useful than our current understanding of fracture mechanics?
• There are many examples in science of the utility of overly simple (and incorrect) models which give us extraordinary insight into complex physical phenemona---for instance, the Bohr Atom. Is this the case for our applications of fracture mechanics?

Debate Format:

1. Each of the moderators will have 10 minutes. One will make the argument that "Fracture Mechanics suffices for the purposes of understanding how complex microstructures give rise to observed strength and toughness behavior", and the other will argue that "An entirely new model is required, which handles the complexities of microstructures, to truly develop a predictive model."
2. Each of the Debators will talk for 15 minutes each, articulating their particular viewpoint of the question
3. The Panel moderators will phrase questions (prepared in advance from the electronic forum) and the debators will respond for less than 5 minutes. The debators will know the questions prior to the debate.
4. Questions will be taken from the audience and the moderators will lead the discussion
5. Each of the debators will have 5 minutes to sum up.
6. We will retire to an environment which lends itself to further debate.