Effects of SMA filament surface nano SiO₂ modification on interface bonding strength of SMA/epoxy composites

In order to investigate the interface bonding behavior of shape memory alloy (SMA) filament reinforced epoxy composites, the interfacial bonding strength of SMA filament/epoxy was tested through single fiber pull-out test firstly. The effects of embedding depth on ultimate interfacial bonding strength and the debonding behavior were analyzed emphatically. Then, using ABAQUS finite element analyses method, the changing relationship of stress distribution versus time during the SMA filament pull-out process was simulated by the element based on surface cohesive behavior. Finally, for the defect of low interfacial bonding strength of SMA/epoxy composites, the method in which nano SiO2 were used to modify the surfaces of SMA filaments was proposed to improve the interfacial bonding strength of materials, and was verified by debonding test. The results reveal that with the embedding depth increasing from 1.0 cm to 1.5 cm and 2.0 cm, the ultimate debonding load increases observably, while the average interfacial bonding strength decreases gradually. When the embedding depth of fiber is 2.0 cm, ultimate debonding appears at 0.300 s. By using the method of coating nano SiO2 particles on SMA surfaces, the surface roughness of fibers can be enhanced, and then improves the ultimate debonding strength of SMA filaments reinforced epoxy composites effectively. The conclusions provide theoretic guidances for the application of SMA filaments in real engineering fields.