Inter-wall bridging induced peeling of multi-walled carbon nanotubes during tensile failure in aluminum matrix composites

• In situ SEM observation of tensile test was performed on CNT/Al composites.
• A multiple peeling phenomenon during MWCNT failure was reported in MMCs.
• Defective structures which bridged walls of MWCNTs were observed by TEM.
• Bridging walls led to effective load transfer between walls and peeling behaviors.

In situ scanning electron microscopy (SEM) observation of a tensile test was performed to investigate the fracturing behavior of multi-walled carbon nanotubes (MWCNTs) in powder metallurgy Al matrix composites. A multiple peeling phenomenon during MWCNT fracturing was clearly observed. Its formation mechanism and resultant effect on the composite strength were examined. Through transition electron microscopy characterizations, it was observed that defective structures like inter-wall bridges cross-linked adjacent walls of MWCNTs. This structure was helpful to improve the inter-wall bonding conditions, leading to the effective load transfer between walls and resultant peeling behaviors of MWCNTs. These results might provide new understandings of the fracturing mechanisms of carbon nanotube reinforcements for designing high-performance nanocomposites.