Effects Of Reinforcing Particle Shape And Distribution On The Mechanical Properties Of Silver Electrical Contact Composites

The SnO2/Ag composite is widely used as electrical contact material because of its excellent arc erosion resistance,weld resistance and abrasion resistance.The electrical contact materials require a certain strength and elastic modulus for various applications.It is known that the volume fraction,particle shape and particle distribution of the particle reinforcement can greatly affect the mechanical properties of the particulate reinforced metal matrix composites.Therefore,this work will study the effects of the volume fraction,particle shape and particle distribution of the SnO2 particles on the mechanical properties of the SnO2/Ag composites through the finite element simulation.Using a three-dimensional multi-particles model,we study the effect of volume fraction of SnO2 on the mechanical properties of the SnO2/Ag composites.It is found that the elastic modulus and yield strength(a0.2)of the SnO2/Ag composites increases with increasing volume fraction of SnO2.When the volume fraction of the SnO2 is 18.3%,the yield strength of the composite increased 14.2%,compared to the 9.5%one.When the volume fraction is 26.5%,the yield strength of the composite increased 27.6%,compared to the 18.3%one.Therefore,when the volume fraction is greater than 18.3%,the increase of the yield strength of the SnO2/Ag composite becomes more rapid.In the study of the effect of particle shape on the mechanical properties of SnO2/Ag composite,the sphere,tablet and rod shape of the SnO2 particle was used as reinforcement.It is found that the rod particle reinforcement has a significant strengthening effect compared to the sphere one,because the rod particle can share more load than the sphere one.Also the tablet particle has a better strengthening effect than the sphere one.It is also shown that the tablet particle not only can share more load,but also can strengthen the matrix.In the effect of the particle distribution of the SnO2 with three different shape on mechanical properties of the composite,it is found that the uniform-distributed particles reinforced composite has a better mechanical response than that by random-distributed particles in all three shapes cases.In the sphere particle case,the distribution effect on the mechanical properties of the composite is less effect.The distribution effect using tablet particles as reinforcement is greater and the distribution effect using rod particles is the most.Furthermore,using the rod particles as reinforcement,the distribution effect on mechanical properties of the SnO2/Ag composites increases with increasing volume fraction of the particles.To study the agglomeration effect of the SnO2 particles on the mechanical properties of SnO2/Ag composites,we design a new model based on the finite element method using a three-region model.The model compares the spacing between the SnO2 particles to judge the particle agglomeration.If the spacing between the particles is smaller than a critical distance,the model will treat them as a particle cluster.Then there will be a new region act on the matrix at the particle/matrix interface between the particles.We define the thickness of the new region is the 2.5%length of the SnO2 particle diameter(about 0.38 μxn)and the mechanical properties is one tenth of the matrix,representing the weakening effect from the particle aggregation.It is found that with increasing the clustered SnO2 particles,the elastic modulus and yield strength of the composites decreased.When all of the SnO2 particles are clustered,the elastic modulus and yield strength of the composites mostly decreased by 27.2%and 30.3%respectively.At present,this model can only qualitatively simulate the effect of the SnO2 particle agglomeration on the mechanical properties of the SnO2/Ag composites,for the capability of the model and the accuracy of the input parameters need to be further valid through the experimental results.