Characterization of change in polypropylene spunbond nonwoven fabric fiber orientation during deformation based on image analysis and Fourier transforms

Abstract

Changes in spunbond nonwoven fabric structural parameters as functions of deformation are reported, based on microphotographs of the nonwoven fabric structures at various deformation stages and using Fourier transforms. The mechanical behavior of the nonwoven structure was considered in relation to three stages of deformation and expressed in terms of the changes in the fiber orientations according to the orientation angle and degree of deformation. With increasing deformation, the fiber orientations in the internal fabric structures correspond to the applied load directions. It was found that the initial stage of deformation with the maximum material stiffness is not accompanied by a significant change in the fiber orientation. However, fiber alignment in the direction of the applied load was observed in the subsequent deformation steps, which are characterized by low deformation stiffness values. An interpretation of the fiber deformation mechanism in the internal structure of the nonwoven fabric was provided, and a coefficient of anisotropy for the internal structure of the nonwoven material under tension was proposed. Good correlation is found between the structural and mechanical anisotropies of the nonwoven fabric.