Opto-Thermo-Mechanical Characterization of Crazing Phenomena Observed for Isotactic Polypropylene Fibers Using Digital Photoelasticity and the Computed Tomography Techniques

Abstract

Digital photoelasticity was used to characterize the crazing phenomena of isotactic polypropylene (iPP) fibers as a precursor of fracture processes. In this study, the effect of stretching at different rates on the formation of crazes was investigated for the iPP fibers. Also, the influence of drawing the iPP fibers at different temperatures on the formation of the crazes was studied. In addition, the effect of heating the crazed iPP fibers on the formed crazes was characterized using digital photoelasticity. Computed tomography was used to obtain qualitative and quantitative measurements of the crazes densities along the cross-sections of the iPP fibers. Also, the birefringence (Δn) values of the crazes were measured for different conditions of stretching and temperature and compared to the Δn of the bulk material. The photoelastic patterns of the iPP fibers are given for illustrating the crazes behavior in the iPP fibers.