Experimental Study of Mechanical Properties of Multiscale Carbon Fiber-Epoxy-CNT Composites

Recently intensive research has been carried out on carbon nanotube (CNT) based polymer composites. However, in this work the macro scale IM700 carbon fiber (CF) has been integrated with amino modified multi-wall carbon nanotubes (MWCNT-NH2) within LY-556 epoxy matrix to produce three-phase, multi-scale composites, with the applications in missiles. The fictionalization of CNTs has been carried out for improved and consistent mechanical and physical properties. High frequency probe sonication method was used for homogenous dispersion of CNTs. Mechanical characterization of the multiscale composites fabricated by hand layup process included tensile, flexure and inter-laminar shear stress tests. The addition of small amounts of MWCNTs (upto 1.5 weight %) for the fabrication of multiscale composites resulted in a maximum enhancement in tensile strength by 23%, flexural modulus by 35%, flexural strength by 5% and ILSS by 7%. CF/epoxy composites (without CNTs) have also been characterized for comparison with MWCNT-NH2/CF/ epoxy composites. For a more accurate prediction of the Young's moduli of multi-scale composites several micromcchanical models (Voigt-Reuss, Halpin-Tsai, and modified mixture Law) compared with the experimental work. These models have been tested for upto 1.5 weight % of CNTs. The difference of approximate 28% of the values in Young's modulus has been reported in the classical micromechanical models and experimental results and it comes out 11% for CF/epoxy composites as they do not have reinforcement of CNT's within it. In all the classical models, the Young's moduli of the carbon nanotube composites were used as matrix properties.