Design And Development Of Impact Resistant Braided Structural Materials Based On Shear Thickening Fluid

In emergency scenarios such as earthquake rescue,firefighters often face the threat of mechanical object impact,which may cause serious harm to rescue personnel and thus affect rescue effectiveness.At present,the impact resistance of existing protective clothing is relatively poor,so there is an urgent need to develop flexible materials with impact resistance to help reduce the occurrence of such accidents.The research and development of flexible protective materials that combine impact resistance and comfort has always been a focus and difficulty for many scholars.Although the use of shear thickener to prepare impact resistant flexible materials solves the problems of traditional protective materials such as thickness and poor flexibility.However,there are currently some common problems with shear thickeners-flexible protective materials: shear thickeners appear liquid and unstable under normal conditions,and are prone to precipitation in long-term contact with air;The silica nanoparticles will fall off after the material is used for a long time,reducing the protective performance of the material;The exfoliated nanoparticles will cause harm to human body if they contact with skin for a long time.Therefore,this project has designed and developed a flexible protective material for a shear thickener filled woven tube structure.The sealing method inside the tube endows the material with better impact resistance,and the woven structure improves the flexibility of the material.The research content and achievements of the project are as follows:(1)Design of impact resistant woven material schemeBased on the impact resistance mechanism of shear thickener,the influencing factors on the energy absorption and buffering performance of shear thickener were clarified.Based on the theory of fabric structure geometry,the stress characteristics of fabric structure under impact load were summarized.A design method for flexible protective materials with shear thickener filling braided tube structure is proposed based on the application requirements and existing problems of impact resistant flexible protective clothing materials.The shear thickener is filled into a silicone tube for sealing,and then the silicone tube is woven into a twodimensional organizational structure.The inner tube sealing can improve the utilization rate of shear thickening fluid and avoid direct contact with air and skin.It can not only prevent the performance of STF from degrading due to contact with air,but also solve the problem that nano particles fall off and contact with skin,thus harming the human body.The woven structure improves the flexibility of materials.This design method meets the application requirements of impact resistant protective clothing.(2)Finite element simulation and impact resistance mechanism analysis of woven structures.The influence of woven structure on the impact resistance of materials and the impact resistance mechanism of shear thickener in woven structures were studied through finite element simulation.The project mainly studied the impact resistance differences of three types of interweaving point structures: parallel straight line crossing structure,parallel bending crossing structure,and bending crossing structure.The experimental results showed that the bending crossing structure has the highest overall energy absorption rate,the lowest peak bearing capacity of the underlying fabric,and its protective effect is relatively good.In addition,the influence of impact speed on the energy absorption and buffering performance of shear thickener was studied through finite element simulation.The higher the impact speed,the greater the proportion of energy absorption of shear thickener,and the better the protective effect.Finally,a steel plate impact simulation experiment was conducted on a complete plain weave woven material model,and the organizational structure has good protective effects and can absorb 89.35% of impact energy.(3)Preparation of impact resistant woven materialsI have mastered the preparation process and process of impact resistant woven structural materials,and the specific process is as follows: use a syringe to fill the shear thickener into the silicone tube,cover the silicone tube with a layer of knitted tube sleeve to further improve the comfort and impact resistance of the material,and use a self-made woven tube holder for weaving.The test results show that the woven material has good softness,comfortable hand feeling and good wearability.The braided material filled with shear thickening fluid has better compression resistance than the braided material filled with water,and can withstand greater compression load under the same strain,and the protective performance of the braided material with a pipe diameter of 6mm is better than that of the braided material with a pipe diameter of8 mm.(4)Evaluation of Falling Ball Impact ExperimentThe project evaluated the impact resistance of woven materials through a self built drop ball impact device.The falling ball impact device mainly includes three parts: height adjustment rod,adhesive and force measuring platform.The impact speed of the ball is adjusted by changing the height of the ball impact.The impact resistance of the woven material is evaluated from two aspects: the appearance of the adhesive pit and the impact force borne by the force measuring platform.The impact experiment found that the volume of the pit in the adhesive with woven material is significantly smaller than that in the adhesive without woven material.The shear thickener can buffer greater impact force compared to water,and as the impact speed increases,its buffered impact force also increases.This indicates that the greater the speed,the more obvious the energy absorption and buffering effect of the shear thickener,and this trend is consistent with the simulation results.