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Engineering properties of spider silk 189

6.3 Tensile properties and constitutive model

6.3.1 Tensile properties
Although the amino acid composition is known for the seven silks, only dragline and
viscid silk of the seven types of silk have been investigated in detail. The material
properties of spider silk vary from specimen to specimen and the two major silks
used in a spider web have very different mechanical properties, therefore tensile tests
of spider silk fibers display a vast range of stressestrain curves.
Fig. 6.3 shows the typical stress-strain curves of the A. diadematus web silks. The
wet and soft sticky spiral silk of the A. diadematus absorbs energy through large

Figure 6.3 Typical stress-strain curves of Araneus diadematus web silks. (a) MA silk,
(b)the wetsilkofthe flagelliform and aggregate glands that together form the capture spiral
(Vollrath, 2000).