Electric anisotropy of carbon nanofibre/epoxy resin composites due to electric field induced alignment

We report the application of alternating electric fields for the alignment and network formation of carbon nanofibres in an epoxy resin dispersion during curing. In situ optical microscopy verified the electrostatic stabilisation of the fibres in the dispersion and the orientation and agglomeration caused by the electric field. An explanation for the interaction forces between particles and the external electric field is given taking into account electric dipoles induced on the fibres. For the cured composites, the structural anisotropy of the fibre network was evidenced by electrical measurements. A maximal anisotropy for the dc resistivity of about 10 and for the dielectric constant at 1 kHz of about 20 was found for composites with a fibre loading >1 wt.%.