We have studied stab and piercing resistance in the dry and wet state for fabrics designed for manufacture of body armor, and also the effect of the number of layers on the strength of ballistic fabrics.The structure of textile fabrics and articles made from them is determined by three groups of characteristics: the structural elements (yarns, fibers), their relative arrangement, and the interconnections between the elements. The properties and appearance of textile fabrics and articles depend to a significant extent on their structure, and so the structural parameters are standardized and monitored along with the quality indices. The major structural characteristics of fabrics are the shape and linear density of the yarns, their weave, the number of warp or weft yarns per 10 cm of fabric, the coverage, the porosity, the connectivity, etc. (Table 1). Ballistic fabrics considered in this paper were made from rusar yarns.From Table 1 it follows that the highest surface density is seen in fabric 86136, made with the highest warp and weft density. Fabric 84127 has the highest surface density. Fabric 86144 has the highest porosity, while fabric 84127 has the lowest porosity.Mechanical properties are the most important for ballistic fabrics [1]. Tests were conducted on a Series 4411 Instron tester with crosshead speed 100 mm/minute. In Table 2 and Fig. 1, we give the results of determination of the mechanical properties of ballistic fabrics, obtained when testing 1, 3, 4, and 8 layers of a sample of plain-weave fabric 84127, performed with piercing and different stabbing devices.Judging from Table 2, regardless of the crosshead used to damage the fabric, the load also increases as the number of layers increases. The curves given in Fig. 1 show that piercing forces and stabbing loads depend on the number of layers of ballistic fabrics.These dependences are determined by the linear function: y = ax -b for piercing with a pick and stabbing with a knife having a single sharp edge; y = ax + b for stabbing with a knife having two sharp edges, where y is the piercing force or the load during stabbing, N; x is the number of fabric layers; a, b are the coefficients for the linear model. Table 3 shows the results of determination of the mechanical properties of ballistic fabrics, obtained for a combination of 3 different layers.The most effective combinations of three fabric layers are the following combinations: for piercing with a pick, a combination of plain weave + waffle + plain weave layers; for stabbing with a single-edged knife, a combination of waffle + plain weave + waffle layers; for stabbing with a double-edged knife, a combination of waffle + plain weave + waffle layers. Table 4 gives the results of determination of the mechanical properties of ballistic fabrics obtained for a combination of 8 layers: waffle + plain weave + waffle + plain + waffle + plain + waffle + plain.Analysis of Table 4 shows that the load for stabbing a material made of 8 layers with a single-edged knife is twice as high as for stabbing with a...

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Similarity theory and dimensionality analysis was used to establish the dependence of the air permeability on the parameters of the structure of nonwovens. Equations were obtained that allow predicting the air permeability of thermobonded nonwovens with consideration of the parameters of their structure and the pressure differential in performing tests.Thermobonded nonwovens have a complex structure whose parameters are primarily determined by the surface density of the cloth and the linear density of the fibres that form it.However, not only the parameters of the structure but also the pressure differential during testing affect the air permeability of textile materials. We express the effect of the basic factors on the air permeability of nonwoven fabrics with the following equation:), , , , (

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