Preparation Of High-distance Warp-knitted Spacer Inflatable Composites And Its Low-velocity Impact Property

Traditional inflatable materials are mostly prepared from polymer films or composite membranes reinforced with textiles by melting,bonding and other methods.The structural shapes are generally spherical,tubular,or irregular capsule shapes made of the combination of multiple structures.In using,its internal pressure must be balanced through a reasonable envelope surface to achieve the balance state against external loads,which greatly limits the application.How to design and prepare high-distance flat flexible inflatable composites with high resistance to dynamic loads is a problem that needs to be solved urgently.Textile structural material is one of the basic materials for the preparation of inflatable composites reinforcement,which have good structural designability and knitting-formability.Especially,the high-distance warp-knitted spacer fabric is an ideal reinforcement due to its three-dimensional structure and low manufacturing cost.High-distance warp-knitted spacer fabric generally refers to a warp-knitted spacer fabric with a distance more than 65 mm knitted on a large-gauge double-needle bed Raschel warp-knitting machine.It has two surface layers and a core layer with spacer filaments,spacer filaments connect them into a whole with running through the upper and lower layers according to the knitting rule.The fabric has the advantages of flat surface,high strength,good toughness,etc.on account of the tie of spacer filaments to be an ideal reinforcement for the preparation of flexible inflatable compositesAlthough the traditional inflatable materials have been deeply studied in the wrinkle load,bending and compression resistance and other aspects of static load,the research on the resistance of impact load of flexible inflatable composites represented by the high-distance warp-knitted spacer fabric is still in the initial stage.In order to provide more theoretical references and accumulation of experimental data,flexible inflatable composites reinforced with the high-distance warp-knitted spacer fabric were prepared,and its resistance to lowvelocity impact under different parameters was studied in this paper.First,three kinds of high-distance warp-knitted spacer fabrics with different thicknesses were knitted.The surfaces of the fabric were coated with a PVC coating and then bonded with ETFE films to prepare inflatable composites.The tensile,tear,burst and puncture properties of the fabric surface layer and the surface layer of the inflatable composite were tested.The study found that because PVC resin penetrates into the yarn and the resin on the surface of the fabric forms a whole through film formation,it can better transmit part of the stress,so the mechanical properties of the composite membranes have been improved;Secondly,the resistance to low-velocity impact performance of the inflatable composites was tested with different thickness,different air pressure under different impact energy.It was found that the high-distance warp-knitted spacer inflatable composites have good energy absorption characteristics,and the impact threshold loading can be delayed by reducing the air pressure within an appropriate range,as well as reducing the damage area under low impact energy.The thickness of inflatable composites has little effect on the peak impact load,but increasing the thickness will result in the decreasing of energy absorption.These phenomena stem from the energy dissipation and absorption caused by the deformation of the structure of inflatable composites;Then,the finite element model of high-distance warp-knitted spacer inflatable composites under low-velocity impact was established based on the experiment to observe the dissipation of stress wave and the local response deformation of structure,and the calculated results were compared with the experimental results.The results show that the high-distance warp-knitted spacer inflatable composites will produce greater deformation to impact load,which is an important mechanism for its resistance to dynamic load damage.Warp-knitted fabric is an anisotropic material,the stress wave propagates and diffuses along the membrane of the inflatable composite in an approximate elliptical shape during impacting,and it plays an intensive role in enhancing inflatable composite,improving the energy absorption of inflatable composite in resisting impact.The main content of this paper is to prepare high-distance warp-knitted spacer inflatable composites,study its resistance to low-velocity impact performance with different parameters,and establish a finite element model to analyze its deformation response and energy absorption in resisting.It provides experimental data accumulation and theoretical basis for the research gap in the field of dynamic mechanics of flexible composites represented by high-distance warp-knitted spacer inflatable composites,and effectively guide the optimization design and preparation of new textile-structure materials,which has important theoretical significance and engineering value.