Graphite fiber composites interlayered with single-walled carbon nanotubes

A scalable processing method was used to fabricate graphite fiber composites with single-walled carbon nanotubes (SWCNTs) and the microstructures and properties of the fabricated laminates were investigated. SWCNTs were sprayed onto the surface of graphite/epoxy prepreg using an air spray. Interlaminar shear strength (ILSS) tests showed that the air spray processing had minimal effect on the quality of the laminates. Scanning electron microscopy (SEM) studies showed that SWCNTs are distributed uniformly in the plane of the laminate but not in the thickness direction due to low resin flow during cure. At high concentrations (>1.0 wt%), combination of a rather thick band of SWCNTs and low resin flow caused lack of resin inside of SWCNT bundles. The properties positively affected are in-plane shear strength, interlaminar fracture toughness (mode I), compressive strength, and electrical conductivity. Those properties showed improvement particularly when a lower concentration of SWCNTs was used. Fractography study using SEM showed altered crack propagation and crack bridging due to the presence of SWCNTs. The out-of-plane electrical conductivity was improved by 144% for 2 wt% SWCNT samples compared to samples without SWCNTs.