Vibroscope Measurements of the Elastic Moduli of Nylon 66 and Dacron Filaments of Various Draw Ratios

Abstract

By use of the electrostatic vibroscope method, dynamic measurements have been made of the Young's modulus derived from bending and the torsional modulus of nylon 66 and Dacron filaments ranging in draw ratio from one (undrawn) to six. Quasistatic measurements have also been made to obtain the Young's modulus derived from extension. The dynamic values of the Young's modulus increase from draw ratio one to draw ratio six by a factor of 3.5 for nylon 66 and 5.8 for Dacron. The torsional moduli of both filament types exhibit no appreciable changes with increasing draw ratio. The ratio of the Young's modulus to three times the torsional modulus, which ratio is unity for a homogeneous isotropic material with a Poisson's ratio of ½, is about three for nylon 66 and greater than five for Dacron at a draw ratio of six. These results, along with those obtained at lower draw ratios, indicate that both filaments become progressively anisotropic with drawing, the extent of the anisotropy reflecting mainly the changes in the Young's modulus. As a check on the experimental procedures, the elastic moduli have also been measured for a 1-mil drawn tungsten wire.