Stress transfer in polyacrylonitrile/carbon nanotube composite fibers

Abstract

Gel spun polyacrylonitrile/carbon nanotube (PAN/CNT) composite fibers have been produced, and the stress-induced G′ Raman band shifts in the CNTs have been monitored to observe stress transfer during fiber strain. Improvements in CNT quality, CNT dispersion, and post-processing fiber drawing are shown to increase the stress transfer from the matrix to the CNT. Radial breathing mode (RBM) intensity of specific CNT chiralities confirms CNT debundling during fiber processing. During PAN/CNT fiber straining, there reaches a plateau in the CNT G′ downshift, signifying that the stress on the CNT is maintained despite continued straining of the PAN/CNT fiber. Correlating CNT strain with CNT modulus and volume fraction allows for the interfacial shear strength (τi) of the PAN-CNT interface to be determined. The as-spun and fully drawn PAN/CNT-A (99/1) nano composite fibers exhibit τi of 13.1 and 30.9 MPa, respectively, while an improved CNT dispersion (PAN/CNT-A (99.9/0.1)) results in τi equal to 44.3 MPa.