Axial Deformation of Dragline Silk of N. Clavipes

Fibers of the silk were obtained by artificial mechanical silking of the female spiders at a rate of 1.1 cm/s. The spiders were obtained from Panama and kept in individual boxes at 24.5–25°C, 36–42% RH under a combination of North window and cool white fluorescent light. They were fed approximately one cricket per day and lived their normal life span. The fibers were kept out of UV and elevated temperatures. The crystal orientation function was measured as a function of the engineering tensile strain on a bundle of fibers. Single fiber birefringence measurements were made as a function of both the axial compressive and tensile engineering strains. The tensile data exhibited evidence of incipient failure at higher strains; hysteresis if the engineering strain is reduced; and a lower failure engineering strain than is often quoted. The hysteresis is attributed to various aspects of relaxation effects and to possible internal structural change in the silk. The fibers which were axially compressed five percent exhibited no failures.

Dedicated to Professor Phillip H. Geil's seventy‐fifth birthday.

Keywords:

• dragline silk
• tensile
• compression
• birefringence
• X‐ray
• hysteresis
• relaxation

Acknowledgments

The authors thank the U.S. Army Research Development and Engineering Center in Natick, MA for the spiders. They thank Associate Dean Ernst D. von Meerwall of the University of Akron College of Polymer Science and Polymer Engineering for his helpful advice with respect to weber.19

Notes

Dedicated to Professor Phillip H. Geil's seventy‐fifth birthday.