Air Permeability of Multilayer Needle Punched Nonwoven Fabrics: Experimental Method

In many applications, fabric structure has a dominant influence on the performance characteristics of a material, particularly in controlling transport of flows. Experimental air permeability was determined for 12 multilayer, heterogeneous, needle punched nonwoven materials. Samples were produced using multiple layers of ceramic and glass fibers. The fibers used to produce the ceramic layers for all samples have approximately the same diameter and density as the fibers used to produce the glass layers for all samples. Therefore, the samples were assumed to be multilayer homogeneous fabrics. In this paper, the experimental permeability is measured usingstandard equipment and results are discussed as a function of fabric construction parameters. Results showed that increasingthe fraction of glass and/or the fraction of ceramic content, and increasingthe number of needle barbs all cause a decrease in air permeability. Statistical results showed that the experimental air permeability can be predicted with greater than 99% confidence when using fabric thickness, fraction of glass in the sample, and fabric density as independent variables in the model.