Flow Resistance
Measure of how easily a fluid moves through a porous textile structure perpendicular to the plane of the fabric. In technical textiles, transverse hydrodynamic permeability determines the efficiency of filtration systems and the performance of composite reinforcements. Liquid forced through the thickness of the material encounters resistance from the individual fibres and the interlacing pattern of the yarn.
The resulting flow rate is a function of the pore size distribution and the overall thickness of the fabric layers.
Structural Variable
Density of the weave and the shape of the yarn cross section influence the path that the fluid must take. High levels of transverse hydrodynamic permeability are preferred in applications like liquid molding where resin must saturate the fabric quickly.
Pressure Differential
Testing involves applying a known pressure across the specimen and measuring the resulting volume of fluid that passes through. Technicians use Darcy’s law to calculate the permeability constant based on the viscosity of the fluid and the dimensions of the sample.
Operational Limit
Compression of the fabric during the test can reduce the pore volume and alter the results. Accurate transverse hydrodynamic permeability data is obtained by maintaining a constant thickness throughout the measurement process.
