Effect of multi-walled carbon nanotubes on mechanical properties of Ti-carbon fiber/polyimide by monomer polymerization super hybrid composite laminates

In order to improve the bonding strength of Ti/polyimide by monomer polymerization (PMR) resin interface and improve the mechanical properties of Ti-carbon fiber(CF)/PMR super hybrid laminates, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of Ti-CF/PMR super hybrid laminates was investigated in this paper. The MWCNTs with different mass fractions (0wt%, 2.5wt%, 5.0wt% and 7.5wt%) were uniformly dispersed in PMR resin by ultrasonic dispersion. The mode Ⅰ interlaminar fracture toughness tests were experimentally conducted to explore the effect of adding MWCNTs on the interface properties of Ti-CF/PMR super hybrid laminates. Then the MWCNTs of optimized content was added to the PMR adhesive layer and CF/PMR resin to conduct bending test so as to explore the effect of adding MWCNTs on the mechanical properties of Ti-CF/PMR super hybrid laminates. SEM was used to investigate the interface morphology and enhancement mechanism of Ti-CF/PMR super hybrid laminates. The results reveal that the mode Ⅰ interlaminar fracture toughness of the PMR adhesive layer for Ti-CF/PMR super hybrid laminates is improved by 74% with 5.0wt% MWCNTs; when 5.0wt% MWCNTs are added into both the PMR adhesive layer and CF/PMR resin, the bending property of Ti-CF/PMR super hybrid laminates is improved by 42% compared with those without adding MWCNTs. This is because the MWCNTs are uniformly dispersed in the PMR adhesive layer and CF/PMR resin, and it can disperse and bear the load transferred from the interface layer to the fiber layer, using its own pull-out, fracture, bridging, debonding to absorb and consume the fracture energy to further improve the bending performance of the Ti-CF/PMR super hybrid laminates.