Stress transfer in polyacrylonitrile/carbon nanotube composite fibers

Abstract

arbon nanotubes (CNTs) are known to act as stress sensors, which can be monitored through the peak shifts of the Raman bands (D, G, and G'). Gel spun polyacrylonitrile/few-walled carbon nanotube (PAN/FWNT) composite fibers have been produced, and the stress-induced Raman band shifts in the FWNTs have been monitored to observe the stress transfer during fiber strain. Improvements in FWNT quality, enhanced FWNT dispersion, and post-processing conditions (fiber drawing) are shown to affect the efficiency of stress transfer from the matrix to the FWNT. Through monitoring of the RBM intensity of specific chiralities, the debundling of the FWNTs can be observed from the raw CNT state, to the solution state, and during the fiber processing stages. As-spun and drawn PAN/FWNT fibers containing 1 wt% FWNT show an increase of 12% and 16% in the tensile modulus, respectively. It is determined that when the stress induced Raman band shift reaches a plateau value as the macroscopic fiber is strained, the PAN-FWNT interface has broken down. Correlating this strain with the stress-strain curve of the PAN/FWNT fiber allows for the PAN-FWNT interfacial shear strength to be determined. The as-spun and fully drawn PAN/FWNT (99/1) fibers exhibit interfacial shear strengths of 13 and 40 MPa, respectively, suggesting that the fiber processing increased interfacial interaction. In addition, improvement in the FWNT dispersion led to a further increase in the interfacial shear strength to 60 MPa.