| Warp-knitted spacer fabric is composed of two surface layers of warp-knitted fabrics and one spacer layer connecting the two surface layers,which has good pressure reduction,vibration absorption,compression resilience,good air permeability,wet conductivity,sound-absorbing and sound insulation properties.So it becomes the optimization of cushion materials,and is gradually utilized as the insole materilas.The paper mainly studies the structure and compression behavior process of spacer fabrics,and aims to supplying a guidance of structural optimization for the design and application of cushion materials,especially for the design and application of insole materials.The main research contents include:(a)three kinds of indenters are chosen to conduct compression on spacer fabrics,including shoe-last compression,spherical compression and plate compression.It is used to analyze effect of indenter shape on compression behavior process of warp-knitted spacer fabrics;(b)by comparing the subjective feeling of foot acting on spacer fabrics with objective compression experiment,their relationship is discussed so as to find out suitable materials for insoles products;(c)the finite element analysis of compression behavior of spacer fabrics,based on the finite element simulation analysis of ABAQUS software,is adopted to analyze the compression behavior and stress distribution of whole spacer fabrics and spacer filament with different structural parameters.The results are as follows:(1)Effect of indenter shape on compression behavior process.The linearity values of compression curves obtained by shoe-last compression are all less than 1,and they show nonlinear rleation of compression curve;the compression curves obtained by spherical compression also have nonlinear characteristics;the compression curves obtained by spherical compression indicate that some samples have linear relations and others have nonlinear trends;through the contrast and correlation analysis of three kinds of compression,there is good correlation between shoe-last compression behavior and spherical compression behavior,poor correlation between shoe-last compression behavior and plate compression behavior,and the correlation between spherical compression behavior and plate compression behavior is significant.So,the compression behavior of shoe-last indenter and spherical indenter is much closer.(2)By having a comparison with the subjective feeling of foot acting on spacer fabrics,it analyzes the feasibility of evaluating the plantar press-comfort performance of warp-knitted spacer fabric by the objective compression curve.Four indexes,namely compression work,recovery work,hysteresis work and maximum compression force,are featured from spherical compression force-displacement curves.The four indexes have high correlation coefficients larger than 0.88 and also have significant relations with the diameter of the spacer filament,fabric thickness,mass and the fabric evaluation score.It is found that the four compression indexes plus the two structure parameters have significant relations with the plantar press-comfort performance and can be used to evaluate the plantar press-comfort performance of warp-knitted spacer fabrics.The sample vectors consist of the compression indexes and structure parameters representing the plantar press-comfort performance of warp-knitted spacer fabric according to the K-means clustering algorithm,and are efficient in objective cluster.Subjective judgments have also been made to group spacer fabrics into three clusters,namely comfortable cluster,moderate cluster and uncomfortable cluster.Comparisons of subjective experimental and clustering results of warp-knitted spacer fabrics indicate that good accordance exists between the subjective judgment method and objective clustering method.It may be possible to show that the compression indexes featured from spherical compression force-displacement curves and structure parameters can be utilized to characterize the plantar press-comfort performance of warp-knitted spacer fabrics and are effective to obtain the fabric evaluation score.(3)The finite element analysis of compression behavior of spacer fabrics shows that the compression work and maximum compression force both become smaller with the increasing of height of spacer fabric when the models are compressed to a certain strain;in addition,the difference of compression work becomes smaller with the increase of height of spacer fabric;the maximum compression force has a similar trend;with the increase of spacer fabrics modulus,the compression work and maximum compression force of the whole model increase,when increasing number of modulus is definite,the increasing number of compression work is more and more small,but the increasing number of maximum compression force have no obvious regularity,and the linear characteristic of model compression,with the increase of spacer filament modulus,first become better and then bad,when the modulus is 3386.7MPa,the linear characteristic of compression curve is best;when other parameters are the same,with the increase of spacer filament density,the compression work and maximum compression force of the whole model become more and more larger,the increasing number of them is more and more larger,and when spacer filament density is small,the linear characteristic of compression curve is good,the nonlinearity is poor;when the diameter of spacer filament becomes larger,both compression work and maximum compression force increase,and in addition to the spacer fabric model with thickness as 5 mm and diameter as 0.2 mm,the nonlinearity of other three kinds of compression curve is better;with the increase of buckling degree of spacer filament,the compression work and maximum compression force of 8 spacer fabric models have no obvious change,and it shows that the compression work and maximum compression force are less affected by buckling degree of spacer filament;when buckling degree is less than 90°,the yield strain of compression force-strain curve appeares in 0.05;when buckling degree is equal to 90°,the yield strain of compression force-strain curve is 0.45;when buckling degree is greater than 90°,the yield strain of compression force-strain curve is 0.40;when there is contact condition between fabric and indenter,the model only have an effect in vertical direction and have no slip and twisting,and surface layer has no irregular deformation due to the bending of spacer filament,however,the error value of compression work,maximum compression force and linearity are between 3.5% and 13%,so the difference between contact condition and non-contact condition is small,and they can be used to explore the compression behavior of spacer fabric models. |
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