I'm getting reports from my tailor about this mailbase - "Never mind the width - feel the quality!"
Perhaps he's right.
It was an interesting exercise to write (or rather, revise in depth) a book after 20 years. What had changed (apart from me)? Well, lots of stuff on molecular conformations and their mechanical implications, quite a bit on nanotesting of one sort and another, a fair amount on computer modelling. Strangely the topics which hadn't moved very much were the calcified materials - bone, especially. I made some enquiries about this and it was confirmed.
Bone hasn't moved much in over 20 years. Nor, for that matter, has mollusc shell. Perhaps the advance is coming with the realisation, which may apply to all biological ceramics, that the matrix isn't a glue - it's a lubricant. Perhaps not throughout the entire volume of the material, but certainly a significant contribution, allowing global strain to double. Strain is then (probably) limited by internal 'imperfections' (i.e. bits which snuggle up to each other in a decidedly non-Cartesian manner) which lock up. Barthelat has shown this in nacre, and bone shows similar behaviour although it hasn't been analysed to the same degree. Which of course ties in with the production of matrix ligaments across the fracture sites. The idea is developed in H. D. Espinosa, J. E. Rim, F. Barthelat and M. J. Buehler, (2009). Merger of structure and material in nacre and bone: Perspectives on de novo biomimetic materials. Progress in Materials Science, 54: 1059-1100.
I know that's a few years ago now, but who is applying these ideas in technical composites?
Answers on the back of a $1000 note, please, to the following address:
Julian Vincent
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"Structural Biomaterials" now out: http://press.princeton.edu/titles/9774.html
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