Nanoscopic observations for evaluating the failure process of aligned multi-walled carbon nanotube/epoxy composites

Abstract

This study examined the nanoscopic damage progression of aligned multi-walled carbon nanotubes (CNT) / epoxy composites under tensile loading using transmission electron microscopy (TEM). Aligned CNT/epoxy composite films (30 micro meter thickness) were processed using a forestdrawn aligned CNT sheet and hot-melt prepreg method. Four film specimens, respectively subjected to tensile stress of 0 MPa, 45 MPa, 95 MPa and 110 MPa, were prepared. After tensile loading, each specimen was machined until the thickness became about 100 nm using a focused ion beam milling machine (FIB) for TEM observations. Damage of three kinds, i.e. CNT break derived from the disordered CNT structures around metallic catalyst, sword-in-sheath type CNT break, and several patterns of interfacial debonding, was observed clearly. The broken CNTs and interfacial debonding per unit area were counted from TEM photographs. Results show that broken CNTs and interface debonding increased considerably at 95-110 MPa, which suggests multiple fracture of CNT under tensile loading. The CNT length at the failure stress (110 MPa) was approximately 45 μm. Estimated values from the strength of CNTs resemble those from macroscopic stress-strain behavior.Nanoscopic observations for evaluating the failure process of aligned multi-walled carbon nanotube / epoxy composites AbstractThis study examined the nanoscopic damage progression of aligned multi-walled carbon nanotubes (CNT) / epoxy composites under tensile loading using transmission electron microscopy (TEM). Aligned CNT/epoxy composite films (30 m thickness) were processed using a

Mechanical performance of epoxy matrix hybrid nanocomposites containing carbon nanotubes and nanodiamonds

“…up to 8.0wt% but the extent of improvement, i.e. 65% [62] and 80% [40] was not comparable in relation to the quantity of MWCNTs used. In an interesting study on three types of CNTs, tensile strength was reported to increase by adding 0.5-1.0wt% SWCNTs, DWCNTs and MWCNTs individually in epoxy matrix composites; the composites containing DWCNTs showed the maximum relative improvement [41,42].…”

“…4 c). Both increasing [63] and decreasing [40] trends have been reported about the fracture strain after incorporating MWCNTs and NDs in polymeric matrices. For example, an increase in fracture strain was observed by adding up to 1wt% MWCNTs [38] and in another study, surprisingly, fracture strain up to 20% was observed in epoxy matrix composites containing 8.0wt% MWCNTs, which increased continuously from ~9% in neat epoxy specimens [62].…”

“…4 b. Generally a rising trend is observed in tensile modulus of epoxy matrix composites by adding CNTs [39,40,64]; for example, the elastic modulus increased continuously in composites containing coiled CNTs [60] and SWCNTs, DWCNTs and MWCNTs, both un-treated and NH 2 -treated, increased the tensile modulus of epoxy matrix composites [41,42]. In an interesting study, 0.5wt% MWCNTs were incorporated in epoxy matrix with different matrix stiffness values by varying the quantity of curing agent; it was found that the effect of MWCNTs was significant in ductile matrix which gradually reduced with an increase in the stiffness of the matrix [65].…”

“…For example, improvement in tensile properties has been shown in epoxy matrix composites containing CNTs in limited quantities, i.e. up to 2.0wt% [38][39][40] as well as in large quantities, i.e. up to 8.0wt% [40].…”

“…up to 2.0wt% [38][39][40] as well as in large quantities, i.e. up to 8.0wt% [40]. The three types of CNTs, i.e.…”