Interface Design And Leakage Performance Analysis Of Polyethylene/Carbon Fiber Composite Materials For Pressure Vessels

Lightweight technology can reduce the weight of the structure,save fuel and increase the load,having more and more applications in the industry.It is a very important research trend today.Therefore,many researchers have focused their research on lightweight composite pressure vessels.Especially the type IV pressure vessel lined with plastic.This project plans to select polythene as the lining.Although the polymer-lined pressure vessel is light in weight,it has the following disadvantages: First,polyethylene plastic is a hard-to-stick plastic,the surface is chemically inert,and the interface between carbon fiber composite material is far inferior to the combination between metal and composite material,which makes it difficult for the fiber layer of the pressure vessel to play a bearing role.Secondly,there are few related studies on the gas barrier properties of polyethylene and its composite materials.It is necessary to study whether the inner liner can still block the movement of permeating gas under a certain pressure,and analyze the movement mechanism of gas molecules in the material.Based on the above two points,the main research contents of this paper are as follows.First of all,in this paper,the surface of the high-density polyethylene is treated by liquid-phase oxidation and plasma treatment,and the surface of the material is characterized.Observe the surface morphology of the material by scanning electron microscope(SEM),Fourier infrared FTIR analysis of possible functional groups on the surface of the material,contact angle experiment to observe the change of the wettability of the surface of the material,and use a universal testing machine to test the interfacial shear force between polyethylene and carbon fiber plates.Secondly,Materials Studio 2018 was used to simulate the permeability coefficient and trajectory of helium in different states.Monte Carlo(MC)method and molecular dynamics(MD)method were used to obtain its solubility coefficient and diffusion coefficient,respectively,and to draw molecular trajectory.Through this simulation,the movement mechanism of gas molecules in polyethylene is analyzed from a microscopic perspective,and the influence of graphene filler and gas pressure on the gas barrier properties of polyethylene is explored.Finally,the subject intends to design a helium leak detection device that can be connected to a gas cylinder and a helium leak detector to test the gas barrier properties under a certain gas pressure.CFRP made by T-700 carbon fiber and E-51 epoxy resin,surface-modified high-density polyethylene,and epoxy resin adhesive were used to make helium leak test samples,and a helium leak test was conducted.Combined with the graphene/polyethylene composite materials that have been studied in our lab before,the effect of adding polyethylene with different graphene content on the barrier properties of helium gas was analyzed;the barrier properties of polyethylene against helium gas at different pressures were also studied.Compared with the above simulation results,the similarities and differences between the experimental and simulated values are analyzed.