Determining the Orientation and Interfacial Stress Transfer of Boron Nitride Nanotube Composite Fibers for Reinforced Polymeric Materials

Boron nitride nanotubes (BNNTs) are promising nanofillers in polymer nanocomposites due to their high strength and high modulus as well as thermal and chemical stability. In BNNTs nanocomposites, the orientation of BNNTs and interfacial stress transfer between BNNTs and the matrix determine the nanocomposite performance. In this study, Raman spectroscopy was used to measure the orientation of BNNTs and interfacial stress transfer of BNNTs in polyacrylonitrile (PAN) fibers. The orientation of BNNTs in the nanocomposite fibers could be tuned by postdrawing fibers, and fibers with higher draw ratios show higher BNNTs orientation. In addition, fibers with higher draw ratios show a higher Raman band shift rate than that of low draw ratio fibers, which indicates enhanced interfacial shear stress between the PAN matrix and BNNTs. This study shows that highly oriented BNNTs are critical to the mechanical properties of the BNNTs reinforced polymer nanocomposites.