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

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This paper presents effects of carbon nanotube (CNT) orientation angle distribution on elastic moduli of aligned CNT/epoxy composites that were fabricated with various volume fractions using hot-melt prepreg method. Tensile testing was conducted to evaluate the composites' mechanical properties. The composites' Young's moduli increased with increasing CNT volume fraction. Scanning electron microscopy (SEM) revealed CNT orientation angle distribution data for the surface and through-thickness planes. The standard deviation of CNT orientation angle distribution was about 30 deg for the surface, and 22.5 deg for the through-thickness plane. The effective Young's modulus of CNT was estimated using the equivalent inclusion theory (Eshelby/Mori-Tanaka theory) incorporating a three-dimensional

Stress transfer efficiency for 60 walls multi-walled carbon nanotube (MWNT) was calculated by the shear-lag theory. The results indicated that stress transfer between walls is insufficient at several tens of nanometer from the end; however stress converged to the same value for adequate length. Effective young's modulus was also calculated and indicated that MWNT can be treated as short fiber for over 20 m length (Aspect ratio > 400). The results implied that interfacial slippage or debonding area exists at the end of the MWNTs. Calculated results, including the alignment and interfacial strength between carbon nanotube (CNTs) and polymer, were compared to the mechanical

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