An investigation of Mode I and Mode II fracture toughness enhancement using aligned carbon nanotubes forests at the crack interface

Abstract

A novel approach for introducing aligned multi-walled carbon nanotubes (MWCNTs) in a carbon-fibre composite pre-impregnated (prepreg) laminate, to improve the through-thickness fracture toughness, is presented. Carbon nanotube (CNT) 'forests' were grown on a silicon substrate with a thermal oxide layer, using a chemical vapour deposition (CVD) process. The forests were then transferred to a pre-cured laminate interface, using a combination of pressure and heat, while maintaining through-thickness CNT alignment. Standard Mode I and four-point bend end-notched flexure Mode II tests were undertaken on a set of specimens and compared with pristine specimens.Mode I fracture toughness for T700/M21 laminates was improved by an average of 31% while for T700/SE84LV specimens, an improvement of 61% was observed. Only T700/M21 specimens were tested in Mode II which yielded an average fracture toughness improvement of 161%. Scanning Electron Microscopy (SEM) showed good wetting of the CNT forest as well as evidence of penetration of the forest into the adjacent plies.

Influence of graphene nanoplatelets on modes I, II and III interlaminar fracture toughness of fiber-reinforced polymer composites

“…As a result, various types of nanoparticles, such as carbon nanotubes (CNTs), have been included in epoxies in an attempt to enhance their toughness [3][4][5]. Indeed, CNTs have been widely used to enhance the fracture response of FRP under modes I and II fracture [6][7][8][9].…”

Crush responses of composite cylinder under quasi-static and dynamic loading

“…T700/M21 prepreg has a relatively high fibre volume fraction due to its unidirectional nature. Hence the overall properties of the shear [34]. As the laminate was composed of equal amounts of 0 and 90 degree plies, the bulk of the energy absorption will be attributed to the fibre-dominated failure mode for a given volume of laminate crushed.…”

Lack of statistical rigor in composite materials experimentation and lessons learned from the science of medicine

“…In those articles that were likely to contain appropriate content, the article was evaluated in detail to establish compliance with the selection criteria and, if so found, to evaluate the statistical rigor as described in section IID. Of the 82 articles, 26 were found likely to have appropriate content and 17 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] were systematically evaluated after being found to meet the selection criteria.…”

“…[4,13] Eight papers [2, 3, 7, 8, 10, 11, 14-16] used 3 specimens or fewer specimens to establish at least one reported mean. One paper [2] used each of {2,3,4,5,6} specimens to establish mean values for the 6 groups. (There is no reason why each group need be the same, however, the smaller samples sizes and inconsistency cause concern.)…”