Hi Ross,

I'll keep this brief because we're deviating a bit from George's post, and I think he's lost interest anyway!

The reason things pass vibration along their structure is due to the level of damping. Highly damped materials such as wood, don't 'ring on' or let the vibration travel very far through them because the small movement of the fibres creates heat and the wave quickly runs out of energy. Lowly damped materials, such as a steel bar, will pass this vibration through the structure without much loss. But if you add external damping to the steel, it will be just as stiff, but not vibrate so much. So stiffness and vibration can be seperate, but a highly damped structure will always vibrate much less because damping is the controlling factor for vibration propagation.

I think that the bottom line is though, getting back to George's post, is that we're all a bit worried about the use of perspex for a structural item, which is exposed to repeated vibration inputs from the cutter etc. I don't know enough about perspex specifically to comment on the stiffness/damping/cracking question, but wish George well with the idea . . .