Interferometric detection of structure deformation due to cold drawing of polypropylene fibres at high draw ratios

Abstract

A stress–strain device was attached to a two-beam polarizing interference microscope to investigate the structure deformation associated with fibre cold drawing. A polypropylene fibre was stretched at high draw ratios, D>6, and the interference patterns were automatically digitized and stored in computer storage media. The microinterferograms show that there are two different mechanisms that occur when the fibre is stretched, depending on whether with fast or slow drawing. In case of slow drawing, smooth deformation was detected, and in case of fast drawing, microcrack deformation was presented. The refractive indices and birefringence of the fibre were measured as a function of draw ratio. The refractive index profiles using fringe image analysis were calculated in cases of fast and slow drawing. The two-beam interferometric technique is a good technique to investigate and detect microcrack deformation across the diameter of a fibre. Microinterferograms are given for illustrations.