The Research Of Weft-knitted Biaxial Fabric Reinforced Advanced Fire-fighting Helmet Shell Material

Aiming at the current problems of domestic and foreign fire helmets in adapting to harsh environments and long-term wearing comfort,and in order to improve the work efficiency and safety level of fire helmets,this article develops an advanced fire helmet shell materials research.Carbon fiber and glass fiber mixed multilayer biaxial weft-knitted(MBWK)fabrics were prepared,and fire-resistant helmet shell materials were developed using them as reinforcement framework materials.The hemispherical surface is used to simulate the surface of a helmet shell,and for the first time,a research on the molding performance of MBWK fabric based on shrinkage is proposed.Based on the Levenberg-Marquardt algorithm,a model of MBWK fabric hemisphere forming was established,which proved the feasibility of the surface forming of flat fabrics.In order to improve the protective performance of fire helmet shell materials,PA/PU micron-sized short fibers were added for the first time in the preparation of composite materials,and their mechanical properties and thermal stability were studied.The results show that the function models of the number of fibers of the MBWK fabric passing through the sphere section surface and the shrinkage based on the Levenberg-Marquardt algorithm is effective and accurate within a certain range of sphere diameters.In the tensile experiment,the added content is The elastic modulus of 2.5% PA/PU short fiber reinforced composites is 53.91% higher than that of pure resin cast bodies.It shows that PA/PU short fiber can improve the elastic deformation resistance of the material.In the impact test,the maximum impact load of the MBWK fabric reinforced composite material with PA/PU short fiber added 45% fiber volume is the largest,which is higher than that of woven fabric reinforced composite.The material is increased by 0.59%,which is 5.81% higher than MBWK fabric reinforced composites.The MBWK fabric-reinforced composite material with a fiber volume content of 35% added PA / PU short fibers has the largest energy absorption,which is2.55% higher than the woven fabric-reinforced composite material and 0.77% higher than the MBWK fabric-reinforced composite material.It shows that the addition of PA/PU short fibers can improve the impact resistance of the material;in the thermal stability performance test,MBWK fabric reinforced composites with fiber volumecontent of 35%,45% and 55% before and after adding PA/PU short fibers,their materials Residual quality has been improved by 24.35%,13.65% and 0.75%,respectively.It is shown that PA/PU short fibers can improve the thermal stability of the material.Finally,MBWK fabric-reinforced composite material with a fiber volume content of 35% and an optimal addition of 0.5% PA/PU short fibers was selected as the shell of the fire helmet.The material is tested for flame retardancy.The limiting oxygen index of the material is 32.7,which indicates that it has excellent flame retardancy.In this paper,the preparation scheme of fire helmet shell material with better protection performance was finally researched.The successful development of the fire helmet shell material can not only further protect the personal safety of firefighters,but also provide the work efficiency of firefighters.There are also socio-economic benefits,which will effectively reduce the gap between domestic and foreign fire helmets,accelerate the upgrading of protective equipment for fire forces,and meet the needs of fire forces.