Determination of Elastic Modulus of Spider’s Silks

Abstract

Elastic moduli were determined from the stress–strain curves of draglines secreted from Nephila clavata spiders (Japanese golden-web spiders) collected at different stages of growth. In order to accurately determine the elastic modulus it was necessary to measure the cross sectional area of the same dragline consisting of double filaments used for measuring the stress–strain curves. The elastic modulus was determined to be ca. 10 GPa for spiders weighing less than 50 mg, ca. 13 GPa for spiders weighing between 50 and 800 mg, and ca. 10 GPa for old spiders weighing more than 800 mg. The relatively small values of ca. 10 GPa for the elastic modulus may come from the relatively large cross sectional area of the draglines for spiders weighing less than 50 mg and from the small value of the elastic limit strength for spiders weighing more than 800 mg. It was found that the elastic modulus of spider’s draglines consisting of almost amorphous protein molecules was relatively large in comparison with the elastic modulus of several GPa obtained for amorphous synthetic polymers.