The strength of spider silk

Abstract

Tensile tests have been made on the draglines of the Queensland Bird-Catching Spider (Nephila maculata): the masses of the several spiders varied by a factor of about 25. The nominal fracture strength of the silk was independent of the spider size and was about 1100 MPa (the true fracture strength was about 1500 MPa). Larger spiders extruded proportionately thicker draglines and the maximum force which a dragline could sustain was generally two or three times the body weight of the spider. Draglines consisted of two or four individual threads and some tests were made of the properties of these constituent strands. Tests made on draglines aged for 21 days showed only a moderate deterioration in properties although a marked change occurred in the initial part of the stress-strain curve.