Microstructure and mechanical characterizations of buckypaper and carbon fiber hybrid composites

Carbon nanotube (CNT) buckypaper possesses excellent mechanical and physical properties which show great potential for use in the fabrication of multifunctional structural composite materials. This paper reports on a study of CNT buckypaper integrated into traditional carbon fiber composites to create interply hybrid composite materials with high CNT content. The quality of hybrid composites was analyzed by investigating different manufacturing parameter setups of autoclave processes, nano/micro resin flow behavior, and the influences of process and structural parameters. Tensile properties and failure modes of the resultant composites were studied. The study found that resin bleeding along the through-thickness direction was inhibited due to extra-low permeability and high resin absorbing capacity of the buckypaper, which was the major contributing factor to void formation and resin starvation defects. Buckypaper/resin layers showed consistent thicknesses in all hybrid composites, which were about double the thickness of the dry, pristine buckypaper due to absorbency and swelling effects. Control and hybrid composites showed similar local fiber volume fractions in the carbon fiber plies. The buckypaper/unidirectional carbon fiber hybrid composites with 4.95 wt% CNTs showed the tensile strength and modulus of 2519±101 MPa and 149±18 GPa, respectively, which are only 4.1% and 6.3% reductions, respectively, compared to the control sample. In contrast to the explosive failure mode of the unidirectional control sample, delamination was the main failure mode for the BP/CF hybrid composites.