Through-thickness air permeability of woven fabric under low pressure compression

Through-thickness permeability (TTP) is one primary property of technical textiles used in air-related applications, such as filtration and protection. The TTP depends on the textile geometrical factors and usually varies according to the test conditions. In this article, the effect of low air pressure compression (LPC) on TTP of woven fabric was investigated. Nine woven fabrics were measured for the relationships of LPC and thickness, LPC and fabric in-plane dimensions, air pressure drop (APD) and air velocity, as well as LPC and fabric TTP. A dramatic decrease of woven fabric thickness was found below the APD value of 200 Pa and less decreased thickness was observed with a continued increase of APD. The variation of fabric in-planar dimensions was found to be negligible during LPC. The plot relationship of the APD and measured air velocity was presented in linearity for most fabric samples. The fabric TTP showed a linear proportion to the fabric thickness, indicating the fabric to be more permeable with the increase of thickness. A sensitivity study showed an evident difference between using fabric constant and decreased (LPC) thickness in calculating TTP, disclosing the importance of compression in fabric TTP evaluation.