Numerical Simulation Of Compression And Ventilation Performance Of Large Mesh Warp-knitted Spacer Fabric

Large mesh warp-knitted spacer fabric has been used in automobile seat ventilation system because of its excellent compression resistance and ventilation performance.The structure of spacer fabric affects its compression performance,and the architecture of spacer fabric after compression determines its ventilation effect.Through the rational fabric structure design,the spacer fabric can achieve high support and high ventilation,which is of great significance to optimize the comfort of the car seat ventilation system.This paper aims to digitally reconstruct the structure of monofilaments of typical large mesh warp-knitted spacer fabric and study the compression mechanism and ventilation behavior of spacer fabric through numerical simulation and experiment.This paper will also explore the relationship between fabric structure,compression performance and ventilation effect,and establish a scheme to optimize the ventilation effect of fabric.The large mesh warp-knitted spacer fabric with was scanned by using of X-ray tomography(μCT),and was reconstructed on the fiber scale.The length,curvature and torsion of the monofilaments were calculated and analyzed.It was found that the curvature curves of the loops were axisymmetric and the curvature of the intermediate points was maximum,while the curvature of the intermediate points of the spacer monofilaments was minimum.The torsion curve of the loops presents sinusoidal distribution,while the torsion curve of the spacer monofilaments presents nonlinear changes.Based on the real geometry model,the finite element simulation software is used for compression simulation.It was found that the mean curvature of the intermediate points of the spacer monofilaments increases linearly during the compression process,while the mean curvature of the intermediate point of the loops increases slightly because the structure of loops is relatively stable.Due to torsion of spacer monofilaments during compression,the sum of the absolute value of the torsion at both ends of the loops and the absolute value of the torsion at the intermediate points of the spacer monofilaments decrease with the increase of the compression degree.During the compression process,the average length of spacer monofilament decreases and its capacity to bear compression load increases.Through fluid simulation,it was found that the air permeability of spacer fabric is high in course direction and low in thickness direction.Before compression deformation of 40%,the permeability of spacer fabric decreases due to the increase of monofilaments density with the increase of compression degree.The smaller the flow rate of the fluid,the greater the pressure.The pressure difference generated by the fluid will affect the shape of the spacer fabric.The change architecture of fabric during compression will affect the ventilation effect of fabric,while the pressure generated by flow field will also affect the architecture of fabric.This paper reveals the relationship between fabric structure,compression performance and ventilation effect,which provides theoretical support for optimizing the comfort of automobile seat ventilation system.