Study On Mechanical Properties Of TiB_x（x=1,2）/Cu Composites Based On Cohesive Model

Particle reinforced copper matrix composites can meet the needs of electronics and power industries due to their good comprehensive mechanical properties.Usually,the failure of matrix,reinforced phase and interface between particles and matrix are condsidered as the main forms of damage failure for Cu matrix composites.And the interface phase is a bridge of stress transfer between particle phase and matrix phase,which has a direct effect on the properties of the composites.The results show that the damage and destruction of interface damage accounts for a high proportion in Cu matrix composites.In this paper,the microcosmic components of TiB2/Cu composites are simplified as three phases:the particle phase,the matrix phase and the interface phase;the Cu matrix composite model of three-phase single cell,multi-particle and hybrid reinforcements is established using the finite element software,and the bilinear cohesive model is used to characterize the interface model.Moreover,the whole process from interfacial initial damage to crack complete propagation and interface debonding failure is simulated.The effects of interfacial properties and particle characteristic parameters on the tensile properties,the initiation and propagation of interfacial damage and the internal stress distribution of the composites was investigated.The simulation results show that:(1)The separation process of the interface between particles and matrix can be divided into three parts,at the stage of interface linear load and interface damage evolution,the interface acts as a bridge of stress transfer,and the particles play a role in strengthening the composites by sharing the matrix stress,while at the interface complete separation stage,the interface stress is zero,and the interface can not play the role in load transfer.Moreover,micro-cracks were formed at the interface.(2)Under the same strain condition,the interfacial damage degree of the composite with strong interfacial bonding is weaker than the weak interface,and the interfacial microcrack propagates slowly,which can improve the strength as well as toughness of the material simultaneously.At the same time,as the particle size grow up,the tensile strength of the composites increased with the same increment due to the improvement of the interfacial properties,while when the particle content varied from 1wt.%to 5wt.%,the increment of the tensile strength of the composites increased continuously due to the improvement of the interfacial properties.(3)The particle size has a great influence on the degree of interfacial damage.The smaller the particle size is,the weaker the interfacial damage is,and thus cause the larger range in which the interface can be used as a load transfer medium is,which is beneficial to improve the plasticity and toughness of the composites.The effect of particle content almost have no influence on the degree of interfacial damage while it can be beneficial to improve the strength of the composites.(4)The random distribution and cluster distribution of TiB2 particles almost have no effect on the interfacial damage and tensile properties of the composites while have great influence on the stress and strain distribution in the copper matrix.And the stress on the cluster particles are more uneven,and the particles are prone to cause brittle fracture in the copper matrix composites.(5)The hybrid between of particles and whiskers helps to improve the strength of the material,and the particles help to reduce the stress on the whisker.In the case of the same strain,the interface damage between the whisker and the matrix,which is mainly concentrated at the end of the whisker;the stress on the whisker is much bigger than that on the particles,and the stress concentration in the middle part of the whisker is more serious than other parts.