Temperature-dependent mechanical properties of polyetherimide composites reinforced by graphene oxide-coated short carbon fibers

Graphene oxide (GO) has been well accepted as one novel fiber sizing agent for enhancing the mechanical properties at low temperature or room temperature (RT) of short carbon fiber reinforced polymer composites. But knowledge is still lacking about the mechanical behaviors at elevated temperature of GO-coated short fiber reinforced polymer composites. Here the temperature-dependent tensile properties of GO-sized short carbon fiber (GO@SCF) reinforced polyetherimide (PEI) composites were systematically investigated from -70 degrees C to 170 degrees C. The GO@SCF/PEI composites with varied GO sizing contents were prepared via an efficient injection molding technique. The GO@SCF/PEI composite with 0.4 wt% GO content was shown to be optimal for the tensile strength at RT and thus was selected to investigate temperature-dependent tensile behaviors. The results show that the GO sizing treatment plays a positive role in enhancing the tensile strength of SCF/PEI composites at -70 degrees C and 30 degrees C whereas a negative role at 100 degrees C and 170 degrees C. Morphological observations indicate that the fiber-matrix interfaces are enhanced at -70 degrees C and 30 degrees C but deteriorated at 100 degrees C and 170 degrees C due to the thermal expansion mismatch between SCF (or GO) and PEI. In addition, appropriate empirical equations were established for elucidating the relationships between their strength/modulus and temperature of PEI, SCF/PEI and GO@SCF/PEI composites.