CarbonBrake,
Thanks for your comments. I'm intreagued by the quasi-plastic behaviour beyond the Hooke's law region that you refer to. Can you give me any references to that; I'd like to read up on it. I have to say that my own experience is that in a single event, it is fair to consider composites to display Hooke's law behaviour right up to failure.
In your references to Youngs modulus (and UTS) decreasing with damage, yes I agree. However, to quantify that is very hard and I've always regarded that as being the primary mechanism of composite fatigue, rather than the failure mode in a single overload event which was what I was referring to primarily.
G