Understanding the enhancement of Young’s modulus of macroscopic carbon nanotube fibers after polymer infiltration

Macroscopic fibres of carbon nanotubes (CNTF) are prone to polymer infiltration into their internal pores by capillary forces, often leading to an increase in fibre tensile properties. Here we study CNTFs infiltrated with different polymers via solution infiltration. The results show increases in specific modulus of up to 50 % after polymer infiltration. This increase occurs due to improved stress transfer between load-bearing elements in the fibres, and saturates for a fibre mass fraction of around 0.85. The modulus of the composites fibres can be described by a rule of mixtures considering an effective fibre modulus, higher than that of the dry fibre and dependant on the polymer matrix modulus. The dependence of this effective modulus on matrix properties can be estimated from in situ Raman spectroscopy measurements during axial tensile testing. A comparison of composite fibres with different polymer matrices shows that the rate of downshift of the 2D Raman band increases almost linearly with increasing matrix modulus. Their dependence provide a direct relation between Raman measurements and the modified rule of mixtures, and is thus close to enabling prediction of composite properties in arbitrary matrices.Macroscopic fibres of carbon nanotubes (CNTF) are prone to polymer infiltration into their internal pores by capillary forces, often leading to an increase in fibre tensile properties. Here we study CNTFs infiltrated with different polymers via solution infiltration. The results show increases in specific modulus of up to 50 % after polymer infiltration. This increase occurs due to improved stress transfer between load-bearing elements in the fibres, and saturates for a fibre mass fraction of around 0.85. The modulus of the composites fibres can be described by a rule of mixtures considering an effective fibre modulus, higher than that of the dry fibre and dependant on the polymer matrix modulus. The dependence of this effective modulus on matrix properties can be estimated from in situ Raman spectroscopy measurements during axial tensile testing. A comparison of composite fibres with different polymer matrices shows that the rate of downshift of the 2D Raman band increases almost linearly with increasing...