The effect of fibre swelling on fluid flow in cotton fabrics: An experimental study

Design of hygiene products such as sanitary napkins, diapers, etc. is heavily dependent on the liquid absorption performance of fabrics. As fibres swell upon liquid absorption, their liquid absorption performance changes. Understanding the flow through porous media under swelling conditions has important implications for product design and has yet to be elucidated fully. The goal of our research was to study the effect of fibre swelling experimentally. Cotton is selected as the test fabric as it is commonly used in most hygiene applications. Under swelling conditions, we analysed the effect of swelling on individual fibres, porosity, permeability, and performance of the cotton fabric. Findings showed that upon water absorption, the fibre diameter increased by 10%, porosity decreased by 11%, and permeability decreased by 60% under fully swollen conditions. The porosity reduction is also predicted analytically using the data we obtained from the fibre swelling measurements. In contrast, t predictions of commonly used analytical CFD models showed only a 30% reduction in the porosity. To correct this, we propose two new correction factors to account for effects of inter-fibre interactions on the total swelling rate of fabric. The performance measures of cotton samples under swelling conditions indicated that advancement of the flow front on the lower face was more dominant than the upper face of the sample possibly related to gravity. These experimental data improve our understanding of wicking flow which can help to improve the design of hygiene products and to develop more realistic CFD models.