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Spider silk is one of nature's 'super-materials'. Its remarkable mechanical properties include high extensibility and strength comparable to that of steel. But Markus Buehler and colleagues show that it is not just these virtues that make silk ideal for web construction. Silk's nonlinear stress response — linear at low strain, suddenly softening as strain increases then stiffening prior to failure — is also critical. This behaviour allows webs to keep their shape when experiencing small, distributed loads such as those exerted by wind. But during strong local deformations, such as those caused by falling debris, the geometrical arrangement of the threads and the nonlinear stress response combine to limit damage to the area near the impact site, so that the web remains functional. Credit: S. Cranford, M. J. Buehler/MIT. Dickens (inset): Rex Features.
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发表于 2012-2-3 00:37
