Research On The Interaction Between Cracks And Doped Spheres In Proton Exchange Membrane

The durability of proton exchange membrane(PEM)is one of the important factors affecting the durability of proton exchange membrane fuel cell(PEMFC).The cracks in PEM and the rapid propagation of cracks accelerate the failure of PEM.Controlling or delaying the propagation of cracks is considered to be an important measure to improve the durability of PEM.It is found that the inclusions or holes in the film have an effect on the crack propagation in the film.Based on this property,different kinds of dopants are used to control the cracks in the film.The influence of doping position,radius and elastic modulus on crack growth is studied.The influence ability on crack growth is characterized by crack growth step and maximum action distance.The results show that:(1)The results show that the doping of hard solid ball has "repulsive" effect on crack propagation,and the closer the doping distance is,the more obvious the repulsive effect is;the maximum influence distance of small ball on crack increases with the increase of radius R of small ball,and increases with the increase of elastic modulus ratio of small ball to film,and the change is not obvious after reaching a certain value.(2)Compared with single ball doping,the "repulsive" ability of each ball of array doping is reduced because the force direction of two balls on the crack is opposite,so the force counteracts each other;when the solid balls are arranged along the film thickness direction,the lower small balls have no effect on the maximum action distance;only one solid ball in the film can not meet the requirement of improving the durability,and multiple solid balls are doped at the same time to improve the durability.The distance between the two hollow spheres in the same layer is 4.0 R,and R = 10 μm.the number of doped spheres per unit area is 625.The distance between the doped solid spheres in the film thickness direction is 2.2 R.In fact,there are three layers of doped spheres in the film.The service time of the film is increased by 24.3%.(3)The closer the crack is to the hollow sphere,the greater the "attraction" of the hollow sphere to the crack.The maximum action distance of the small sphere to the crack increases with the increase of the radius r of the hollow hole and the ratio of the modulus.The wall thickness ΔR of the doped small sphere has no obvious effect on the maximum action distance.(4)When the doped spheres are arrayed in the film,when the two hollow spheres are arranged parallel to the middle plane,the maximum action distance is smaller than that of a single hard hollow sphere.This is because the force of the two spheres on the crack is opposite and counteracts each other;the "attraction" effect of the hollow spheres arrayed in the film thickness direction is superimposed.The doping scheme is layered dislocation doping.The distance between two hollow spheres in the same layer is within 4.5 R ～ 5.0 R,and the spacing between each layer is within 2.25 R ～ 2.5R.When the radius of the hollow hole is R = 10 μm,and the wall thickness of the hollow sphere is ΔR = 3 μm,about 400 ～440 spheres need to be distributed in the unit area.In fact,two layers of doped spheres can completely attract cracks and control the propagation.