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Multiscale toughness amplification in natural composites

  • Francois Barthelat (a1), Reza Rabiei (a1) and Ahmad Khayer Dastjerdi (a1)


Hard biological materials such as bone and nacre exhibit remarkable mechanical performance, particularly in terms of fracture toughness, despite the weakness of their constituents. Mechanical performance of nacre and bone can largely be explained through their staggered microstructure where stiff inclusions of high aspect ratio are embedded in a softer matrix. The mineral inclusions provide hardness and stiffness while the organic matrix introduces ductility. The high performance of these natural structures is unmatched by any synthetic ceramic, which therefore makes them a substantial source of inspiration for development of new artificial materials. While the modulus and strength of these structures are well understood, fracture toughness remains unclear and controversial. In this work, chevron double cantilever beam fracture tests show that the interfaces in nacre have a low toughness, comparable to that of the tablets (in J terms). This highlights the important role of structural design on fracture toughness. At the next step, a fracture model is presented to explain the toughness amplification observed in natural staggered structures based on two essential extrinsic toughening mechanisms: crack bridging and process zone. The modeling results show that toughness can be further amplified by incorporating high concentrations of small inclusions with high aspect ratio. This conclusion is applicable to construction and optimization of natural and biomimetic composites.



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1. Wegst, U.G.K. and Ashby, M.F., The mechanical efficiency of natural materials . Philosophical Magazine , 2004. 84(21): p. 21672181.
2. Buehler, M.J. and Yung, Y.C., Deformation and failure of protein materials in physiologically extreme conditions and disease . Nature Materials , 2009. 8(3): p. 175188.
3. Barthelat, F., et al. ., On the mechanics of mother-of-pearl: A key feature in the material hierarchical structure . Journal of the Mechanics and Physics of Solids , 2007. 55(2): p. 225444.
4. Gupta, H.S., et al. ., Cooperative deformation of mineral and collagen in bone at the nanoscale . Proceedings of the National Academy of Sciences of the United States of America , 2006. 103(47): p. 1774117746.
5. Gao, H.J., Application of fracture mechanics concepts to hierarchical biomechanics of bone and bone-like materials . International Journal of Fracture , 2006. 138(1-4): p. 101137.
6. Currey, J.D., Mechanical Properties of Mother of Pearl in Tension . Proceedings of the Royal Society of London , 1977. 196(1125): p. 443463.
7. Gao, H.J., et al. ., Materials become insensitive to flaws at nanoscale: Lessons from nature . Proceedings of the National Academy of Sciences of the United States of America , 2003. 100(10): p. 55975600.
8. Barthelat, F. and Espinosa, H.D., An Experimental Investigation of Deformation and Fracture of Nacre-Mother of Pearl . Experimental Mechanics , 2007. 47(3): p. 311324.
9. Broz, M.E., Cook, R.F., and Whitney, D.L., Microhardness, toughness, and modulus of Mohs scale minerals . American Mineralogist , 2006. 91(1): p. 135142.
10. Khayer Dastjerdi, A., Rabiei, R., and Barthelat, F., Interfacial fracture toughness of nacre. in preparation.
11. Anderson, T.L., Fracture Mechanics: Fundamentals and Applications, 2nd edition. 2nd ed. 1995: CRC Press.
12. Smith, B.L., et al. ., Molecular mechanistic origin of the toughness of natural adhesives, fibres and composites . Nature (London) , 1999. 399(6738): p. 761763.
13. Tvergaard, V. and Hutchinson, J.W., On the toughness of ductile adhesive joints . Journal of the Mechanics and Physics of Solids , 1996. 44(5): p. 789800.
14. Evans, A.G., et al. ., Mechanisms of Toughening in Rubber Toughened Polymers . Acta Metallurgica , 1986. 34(1): p. 7987.
15. Wang, R.Z., et al. ., Deformation mechanisms in nacre . Journal of Materials Research , 2001. 16: p. 24852493.
16. Barthelat, F. and Rabiei, R., Toughness amplification in natural composites . Journal of Mechanics and Physics of Solids , 2011. 59(4): p. 829840.
17. Bekah, S., Rabiei, R., and Barthelat, F., Structure, Scaling and Performance of Natural Micro- and Nanocomposites . Bionanoscience , 2011: p. in review.


Multiscale toughness amplification in natural composites

  • Francois Barthelat (a1), Reza Rabiei (a1) and Ahmad Khayer Dastjerdi (a1)


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