The effect of interfacial microstructures on joining strength of polymer-metal hybrid interface

The high strength steel (HSS) material has high stiffness and strength, which is usually applied in load-bearing structures, but its density is also high. Although the glass fiber-reinforced polymer material has low density and excellent designability, they couldn't be used as a structural element solely due to their low absolute stiffness and strength. Polymer Metal Hybrid (PMH) structure combines polymer with metal and take the advantages of both materials, that could achieve both the light weight and excellent mechanical properties. The main problem of this technology is that the connection strength of the two materials is possibly insufficient. This paper takes the polypropylene/HSS hybrid structure as an example, and studies the influence of interface microstructure on the bonding strength. Four kinds of micro-scale interfacial geometry, the smooth plane, the triangular serrated, the rectangular serrated and the mechanical interlocking, were modeled and compared with each other. Under the bending, tension and shear loads, respectively, the bonding strength were studied using analytical method and finite element simulation. It is found that the microstructure geometry has important effect on bonding strength. When the ratio of polymer modulus to HSS modulus rises, the interfacial strength and ultra load-bearing capability increase. The optimal interfacial microstructure for different loading type will be suggested, which is very useful to the design of PMH structures.