Experimental and simulation investigations of the effect of hybrid GO-thermoplastic polyimide sizing on the temperature-dependent tensile behavior of short carbon fiber/polyetherimide composites

Sizing treatment of fibers is crucial to the interfacial properties and thus the mechanical properties and temperature dependent reinforcing efficiency of short fiber reinforced polymer composites. In this work, polyetherimide (PEI) composites were prepared using highly efficient injection molding technique by introducing three kinds of short carbon fibers (SCFs) treated with graphene oxide (GO), thermoplastic polyimide (TPI) and GO-TPI hybrid sizing, respectively. The effects of sizing agent on the temperature-dependent (−60 °C, 20 °C and 100 °C) tensile behavior of SCF/PEI composites were systematically investigated. The results indicate that the tensile strength of SCF/PEI composites increases with decreasing the temperature due to the higher interfacial clamping stress at low temperature. In particular, it is observed that the hybrid GO-TPI sizing leads to the optimum reinforcement effectiveness, attributing to the blocking effect of GO and the miscibility of TPI and PEI. Single fiber push-in test was conducted and corresponding numerical simulation was made to reveal the effect of GO-TPI sizing on the interfacial properties of SCF/PEI. In addition, the finite element modeling of single carbon fiber composite fragmentation with different sizing treatments was developed to clarify the temperature-dependent mechanical behavior of PEI composites based on the three types of coated SCFs.