Study On Design And Forming Process Of Aramid/Epoxy Flame Retardant Composite Sealed Cylinder

The composite tubular structure is a structural element with a reasonable form of stress.It has good structural stability and high specific strength and specific rigidity.Therefore,it is widely used in military,aviation,construction,medical and health fields.At present,with the improvement of people's safety awareness and the continuous expansion of the application range of composite materials,high flame retardancy has gradually become one of the necessary properties of composite materials.Para-aramid not only has excellent physical and chemical properties,but also has excellent flame retardant and high temperature resistance.In this paper,para-aramid and halogenfree flame-retardant epoxy resin are used as raw materials to design and develop a composite calligraphy and painting storage cylinder with high flame retardancy,compression resistance,sealing and other functions.The main research contents and research results of this article are as below:Molded composite laminates under different molding pressures were prepared.The thickness and fiber volume fraction of the laminate,mechanical properties and metallographic microstructure under different molding pressures were tested and analyzed.The results show that as the forming pressure increases,the thickness of the laminate decreases,the fiber volume fraction increases,the fibers are more densely arranged,the resin-rich area decreases,and the overall mechanical properties increase.When the forming pressure reaches 0.8 Mpa,the comprehensive mechanical properties are optimal.Continue to increase the pressure,the overall mechanical properties decline,and the thickness,fiber volume content,and the tightness of the arrangement and distribution between fibers basically no longer change.The fiber volume fraction of the final product can reach 60%.The flame retardant performance test was carried out on the sample with a molding pressure of 0.8MPa.The results show that the limit oxygen index(LOI)of the laminated board is 44.57%,which reaches the level of flame retardant materials;the vertical combustion performance test results can reach the V-0 level requirements.The sample has excellent heat resistance and flame retardancy.In ABAQUS,a finite element model of radial partial loading of circular tubes with different wall thicknesses is established.The load size is 20000 N,which acts on the quarter arc surface of the cylindrical shell with a length of 225 mm.The maximum stress criterion and the von Mises yield criterion are used to comprehensively judge whether the composite cylindrical shell is damaged under a given load condition.The results show that when the wall thickness is 1.96 mm,the maximum principal stress is 523.5 Mpa,which is greater than the tensile failure stress in the fiber direction of the material,and the maximum shear stress is 36.2 Mpa,which is greater than the shear failure stress of the material.Does not meet the design requirements;when the wall thickness is 2.2 mm,although the thickness meets the design requirements,the maximum principal stress and shear stress of the simulation results at this thickness are closer to the strength limit of the material,and the risk of damage is greater.For safety considerations,this thickness value is not adopted;when the wall thickness is 2.44 mm,the maximum equivalent stress is 341.7 Mpa,which is far less than the material's yield strength of 504.5Mpa;the maximum principal stress is 391.4 Mpa,which is far less than the tensile of the material in the fiber direction The strength is 504.5 Mpa;the maximum shear stress is 26.4 Mpa,which is less than the material's shear strength of 33.0 Mpa,so the design wall thickness of the round tube is determined to be 2.44 mm.According to the design size of the round tube,the aramid composite material round tube was prepared by the autoclave forming process,its radial compression performance was tested and its head design was carried out.The results show that the forming wall thickness of the round tube is 2.46 mm,which is basically consistent with the design wall thickness;its radial compression failure load is 23939 N,which satisfies the design requirement that its radial direction does not cause damage under the load of 20000 N,which can explain the simulation to a certain extent The analysis result has high accuracy;the metal structure head is connected to the two ends of the round tube with an adhesive to achieve sealing,one end is a non-removable oval head,and the other end is a convenient and detachable head with screw connection.