Enhancement of open hole tensile strength via alignment of carbon nanotubes infused in glass fiber - epoxy - CNT multi-scale composites

Cut-out or holes are unavoidable features in composites for structural assembly and functionality. To enhance the strength of the unidirectional glass fiber reinforced plastic (UD-GFRP) laminates around the cut-outs, multi-walled carbon nanotubes (MW-CNTs) were locally aligned at the periphery of the cut-outs via non-uniform electric field. These multi-scale UD-GFRP composites were fabricated in two configurations based on CNT alignment in parallel and perpendicular directions to the glass fiber orientation. The performance was compared with composites containing randomly oriented MW-CNTs in epoxy matrix and composites without MW-CNTs. The damage evolution was investigated using digital image correlation (DIC) techniques during open hole tensile (OHT) tests. The presence of aligned MW-CNTs around the hole perpendicular to the fiber orientation was able to arrest the pertinent damage modes leading to an increase of the tensile strength by 27% as compared to the control samples fabricated using neat epoxy resin.