Three-dimensional nanoprepreg and nanostitched aramid/phenolic multiwall carbon nanotubes composites: Experimental determination of in-plane shear

In-plane shear of nanostitched three-dimensional para-aramid/phenolic composites were experimentally investigated. Adding the nanostitched fiber into nanoprepreg para-aramid fabric preform composites slightly improved their shear strengths. The carbon-stitched composite exhibited comparatively better performance compared to the para-aramid stitched composite probably due to well bonding between carbon fiber and phenolic resin. The stitched nano composites had mainly matrix breakages and micro shear hackles in the matrix; matrix debonding and filament pull-out in the composite interface; fibrillar peeling and stripping on the filaments due to angular deformation. This mechanism probably prohibited extensive interlaminar opening in the nanostitched composites. The result exhibited that the introducing of the nano stitched fiber where multiwall carbon nanotubes were transferred to the out-of-plane of the base structure enhanced its transverse fracture as a form of confined delamination area. Therefore, the damaged tolerance properties of the stitched nano composites were enhanced compared to the base.