The Characterization Of Pressure Relief Of Warp-knitted Spacer Fabric

Warp-knitted spacer fabric is a three-dimensional knitted fabric of sandwich structure,including a bottom layer,an upper layer and a middle layer.Spacer fabric is becoming the preferred structural material in the field of cushion material for good permeability and outstanding pressure relief property.This paper focuses on the pressure relief properties of warp knitted spacer fabric,and explores the relationship between structure and pressure distribution performance,so that it can provide structure optimization guidance for the design and application of cushion material.The main research contents include:(a)Spherical compression and plate compression tests are conducted to analyze effect of structure parameters of spacer fabric on compression performance.(b)The pressure parameters are featured to characterize the pressure performance of spacer fabric.(c)According to the subjective evaluation and characteristic parameters results,they are used to further validate the pressure parameters.The results are as follows:(1)In the process of spherical compression,pressure peak has a great relationship between plate pressure peak and compression work.The spacer filament bear the main pressure.The bigger diameter of spacer filament,the greater the pressure can bear.At the same time,the compression work has a positive correlation with the pressure peak of flat pressure,but the correlation is far less than the relationship between the thickness of the fabric itself.The correlation coefficients of thickness and plate pressure peak are 0.043 and 0.003,the greatest impact on the compression work is the thicknes,followed by plate pressure peak.The correlation coefficients of plate compression work between the diameter of spacer filament,thickness,mesh number,course and plate pressure peak are 0.001,0.037,0.003,0.004,0.004,-0.756.The spherical compression recovery work has a great relationship with plate compression work,followed by the thickness,course density,plate pressure peak,mesh number,the diameter of spacer filament.The normalized coefficients of wale density,weaving angle,filament diameter,thickness and arrangement density are 0.004,-0.003,0.47,0.019 and 0.002,and the diameter of spacer filament is the most important factor of compression recovery rate.The normalized coefficients of diameter,course density,arrangement density,weaving angle,and flat pressure linearity were-0.002,-0.004,-0.003,0.006,and 0.37,and the flat pressure linearity has a great relationship with spherical compression linearity,followed by weaving angle,course density,arrangement density and filament diameter.(2)In order to measure contacting area and characterize pressure-distribution property of spacer fabric,several spacer fabrics are plied.The relationship between pressure and contacting area of different fabrics was studied.It was found that contacting area showed a regular change when the pressure peak was 500 N.Under the same pressure,the larger the contacting area,the smaller the average pression,so the pressure relief performance is better;different spacer fabrics have anisotropy,and the change of contacting area can reveal the change of anisotropy.Spherical compression rate has a good correlation with plate compression rate,plate compression recovery work,plate compression recovery rate and contacting area of spherical contacting area of 52 s,94s and 180 s.Spherical compression work has a good correlation with spherical compression recovery work,spherical compression recovery rate,spherical compression linearity,plate compression work,plate compression recovery rate,plate compression linearity,spherical contacting area of 180 s.Spherical compression recovery rate has a good correlation with spherical compression linearity,plate compression work,plate compression recovery rate,spherical contacting area of 180 s.Plate compression recovery rate has a good correlation with plate compression recovery rate,plate compression linearity,spherical contacting area of 94 s,180s.Plate compression work has a good correlation with plate compression work,plate compression recovery rate.Plate compression recovery work has a good correlation with plate compression recovery rate,spherical contacting area of 180 s.Plate compression recovery rate has a good correlation with plate compression linearity,spherical contacting area of 180 s.(3)By the subjective scoring method,8 volunteers divide the number1 to number12 fabrics into 3 categories through their subjective feelings,the first is very comfortable,the second is basic comfortable,and the third is slightly uncomfortable;based on ranking method,the comfort level of the fabrics are arranged in descending order.The smaller the number is,the more comfortable the fabric is.In order to evaluate the effectiveness of ranking values ofall fabric samples by eight subjects,the effectiveness coefficient,W,of ranking values and Fhypothesis test areutilized according to statistical analysis of subjective judgment method.It indicates that the subjective judgments of pressure comfort by eight subjects are effective.According to K-means clustering method,sample vectoris composed of pressure peak,compression work,recovery work,recovery rate,linearity.Three clusters are objectively formed by K-means clustering algorithm.There exists good consistency between subjective classification and objective clustering.