The Mechanical Properties Of Hair I. The Dynamic Sonic Modulus

Sonic velocity measurements allow instantaneous determination of Young's Modulus of Elasticity during stress-strain testing. These studies can be performed on single human hairs and yield reproducible results. A consistent relationship exists between the sonic velocity and the stress-strain curves of hair. Compared to other materials hair is exceptional with a decrease in Young's Modulus persisting until 25% extension. The sonic velocity curve of hair for its initial 20%–25% extension can be reproduced in isolated α-kerat in filaments, and is not observed in other keratins