Premium
The Effect of Nanotube Content and Orientation on the Mechanical Properties of Polymer–Nanotube Composite Fibers: Separating Intrinsic Reinforcement from Orientational Effects
Author(s) -
Blighe Fiona M.,
Young Karen,
Vilatela Juan J.,
Windle Alan H.,
Kinloch Ian A.,
Deng Libo,
Young Robert J.,
Coleman Jonathan N.
Publication year - 2011
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201000940
Subject(s) - materials science , nanotube , reinforcement , composite number , composite material , orientation (vector space) , carbon nanotube , polymer , nanotechnology , geometry , mathematics
We have measured the mechanical properties of coagulation‐spun polymer–nanotube composite fibers. Both the fiber modulus, Y , and strength, σ B , scale linearly with volume fraction, V f , up to V f ∼10%, after which these properties remain constant. We measured d Y /d V f = 254 GPa and d σ B /d V f = 2.8 GPa in the linear region. By drawing fibers with V f < 10% to a draw ratio of ∼60%, we can increase these values to d Y/ d V f = 600 GPa and d σ B /d V f = 7 GPa. Raman measurements show the Herman's orientation parameter, S , to increase with drawing, indicating that significant nanotube alignment occurs. Raman spectroscopy also shows that the nanotube effective modulus, Y Eff , also increases with drawing. We have calculated an empirical relationship between the nanotube orientation efficiency factor, η o , and S. This allows us to fit the data for Y Eff versus η o , showing that the fiber modulus scales linearly with η o , as predicted theoretically by Krenchel. From the fit, we estimate the nanotube modulus to be; Y NT = 480 GPa. Finally, we show that the fiber strength also scales linearly with η o , giving an effective interfacial stress transfer of τ = 40 MPa and a nanotube critical length of l c =1250 nm. This work demonstrates the validity of the Cox‐Krenchel rule of mixtures and shows that continuum theory still applies at the near‐molecular level.