| Military battle uniform is the necessity for soldiers to wear during a long time training and combat.In summer and winter,in order to keep flexible,the battle uniform was worn closely to human skin and inevitably caused friction.Compared with other general textile,the environment of battle uniform was more complicated,which turned out that the normal load on the friction of skin was larger,the slide speed was faster,and the frequency was higher.This situation was more likely to cause skin damage.In addition,the friction characteristics of battle uniform in wet and dry conditions also had a great impact on comfort when wearing.Therefore,as a kind of functional uniform,the battle uniform was given higher requirements on the friction properties of textile.However,based on its current development,the main considerations in design and production of battle uniform were camouflage,fire resistance,durability,economy and other factors,with few studies on friction characteristics.Thus,it was of great theoretical and practical significance to study the frictional behaviors between battle uniform textile and human skin to optimize the design and to enhance the protection of soldier.In this paper,the interaction between battle uniform and skin under low and high load of the ball-surface reciprocating friction mode was simulated with the UMT-II.Surface topography was observed by Stereo microscope.In order to measure the hydrophilicity,hydrophobicity and water absorption of the textile,video contact angle measuring instrument and electronic weighing apparatus were introduced.The physiological hydration instrument was used to measure the degree of skin hydration under different wet conditions.Results contributed to analyze the influence of the load,friction direction,wet and dry state,and skin hydration on the friction characteristics.It could be a foundation for selecting and improving battle uniform design and manufacturing process.The main conclusions are summarized as below.1.With dry condition,the friction coefficient was significantly related to the surface morphology of the textile when the normal load was 1 N.The friction coefficient of the textile with the twill-weaved structure and smooth surface was lower;with the increase of sliding speed,the friction coefficient increased.Sliding at a low speed would reduce friction between the textile and the skin.The influence of different frictional directions on the friction coefficient was related to the warp and weft density.The coefficient of friction along the meridional direction decreased when the meridional density was higher than the weft density.On the contrary,the coefficient of friction was smaller along the latitudinal direction.When the normal load grew till 5 N,the friction coefficient between the textile and skin increased.The friction coefficient between different textiles was relatively small,and the friction displacement mainly depends on the deformation of subcutaneous tissue.2.With wet condition,the friction coefficient increased compared to the dry condition because of the adhesion between textile and skin.The different friction coefficients were related to the water absorbency of the textile.The stronger the water absorbency kept,the lower the coefficient of friction was.The wet and dry state of the textile had a greater impact on the friction properties compared with the surface appearance of the textile.Therefore,for reducing frictional damage,it was of great importance to maintain battle uniform and skin dry in wearing environment.3.In the textile-water-skin friction interface,skin hydration and textile moisture absorption affected friction properties.With less water on the surface,due to the strong water absorbency of the textile,part of the water was absorbed by the textile,and the rest stayed on the textile-skin surface.Water film tension between the surfaces increased the friction between skin and textile.The skin hydration gained with the increase of the interface water and the real area of friction,leading to the growth of the friction coefficient.When the interface water was excessive,the interface was in completely wet state.A layer of lubricating film formed between the interfaces and the friction coefficient decreased.4.Surface roughness of the skin increased after the friction.Obviously,skin damage caused by the normal load of 5 N was larger than that of 1 N.The textile with long raised fiber and the plain structure was easier to scratch skin,soft cotton,while twill textile could reduce the friction of the skin damage. |
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