Preparation Of Three-dimensional Density Gradient Honeycomb Fabric And Impact Resistance Test Of Its Composites

Equal density honeycomb material has the characteristics of light,high strength,good impact and so on,and it is widely used as energy absorber in various fields.Density gradient honeycomb material is a derivative of equal density honeycomb material,the presence of density gradient can significantly improve the energy absorption of honeycomb materials.This paper is based on the calculation formula of cellular cell under ideal model,and combines the principle of multilayer weaving as well as fabric structure design.By changing the wall length or wall thickness of the adjacent cell and make the density change along the thickness of the fabric,we get two kinds of continuous three-dimensional density gradient honeycomb fabric: density gradient honeycomb fabric with variable size and density gradient honeycomb fabric with variable thickness.The specific design scheme is as follows: at first,the structure diagram along the direction of thickness of the fabric is drawn according to the aperture ratio or wall thickness ratio of honeycomb cellular cell element in adjacent layer;second,according to the schematic diagram of the structure,a cross section diagram of the fabric in a weave repeat unit is drawn when the basic weave adopts the plain and the stitching weave adopts the orthonormal weave;finally,the cross section diagram is converted to the looming drafting according to the order of weft insertion.Because the weaving of honeycomb fabric must adopt multi warp beam to supply warps,in this paper,the yarn consumption of each layer is calculated according to the buckling of warp.In order to avoid the unevenness of tension produced due to the different amount of warp yarn consumption,the same yarn consumption is placed in the same beam and the different yarn consumption is placed in different beam in weaving.After weaving,the vacuum assisted resin transfer molding process(VARTM)is used to compound the fabrics.This paper also analyzes the interweaving characteristics of warp and weft when adopting different basic weave and stitching weave,and design seven kinds of equal density honeycomb fabric when its basic weave adopts plain,twill and its stitching weave adopts plain,warp rib weave,weft rib weave,basket weave and orthonormal weave.These fabrics is made into composite material and the impact test is carried out.The test results show that the energy absorption effect of three dimensional honeycomb composite materials adopting twill as basic weave and stitching weave is better than materials adopting plain.And the order of energy absorption properties of honeycomb materials with different connection structures are: orthonormal weave > basket weave > warp rib weave > weft rib weave > plain weave.In order to explore the influence of different gradient coefficient on the energy absorption properties of honeycomb materials,this paper also design three-dimensional negative gradient honeycomb fabric with cell diameter ratio of 2:1 and 3:1 as well as wall thickness ratio of 1:2 and 1:3 in adjacent gradient layer,then turn the negative gradient honeycomb fabric 180 degrees along the horizontal direction to obtain the positive gradient honeycomb fabric.These fabrics also were made into composite material and the impact test is carried out.The test results showed that the energy absorption performance of positive gradient honeycomb material is better than negative gradient,whether it is variable size density gradient honeycomb material or variable thickness density gradient honeycomb material.And with the enlargement of the cell diameter ratio,the energy absorption property of the materials decreases,while its energy absorption property increases with the increase of wall thickness ratio.