Performance evaluation of unidirectional molds used for measuring saturated transverse permeability of engineering textiles

Transverse permeability measurement of engineering textiles by state-of-the-art approaches revealed considerable discrepancies between different test devices. The absence of performance analysis protocols makes quantifying error sources challenging. This work addresses this issue by providing approaches for evaluating performance of unidirectional test devices and obtaining transverse permeability from conventional saturated tests. Firstly, experiments are presented to illustrate how flow distribution plates affect flow capacity and lead to underestimation of permeability. To quantify this effect and describe device performance, a dimensionless descriptor, discharge coefficient, is introduced. The latter appears to depend on mold geometry and sample thickness and anisotropy. An iterative framework is then established to obtain intrinsic transverse permeability through simulations or using the descriptor. Two molds were investigated with actual textiles. The first underestimated permeability by up to 51%, whereas the second by 36%, resulting in inconsistency. Comparatively, the proposed approach significantly improved measurement accuracy and consistency for both molds.