Mechanical improvement of carbon fiber/epoxy composites by sizing functionalized carbon nanotubes on fibers

The pressure of this vacuum molding process is kept at about 0.5–2.5 MPa to obtain CFRP laminates.   Surface morphologies of the CF after sizing treatments were observed by field emission scanning electron microscopy (FESEM, FEI Nova Nano, 450 microscope), and chemical structure change of MWCNT in the range of 500–4000 cm 1 was conducted with a resolution of 4cm1 by Fourier transform infrared spectroscopy (FTIR, Thermo Scientific, Waltham, MA, USA).   The specimens for three-point bending tests were performed based on the ASTM D7264, which is commonly used for high-performance fibers/polymer composites.29 In each group, no less than five parallel samples were used, and results were calculated by using an average value of these samples.

After the mechanical test, the failure morphologies of the samples were observed by scanning electron microscopy (SEM, Evo-18 Zeiss., Oberkochen, Germany) with an acceleration voltage of 15–20 kV. The ILSS of CFRP was conducted with a loading rate of 2 mm/min based on the ASTM D2344 and by using an electronic universal testing machine (INSTRON 5598, USA).