Effect of sisal fibre orientation on electrical properties of sisal fibre reinforced epoxy composites

Abstract

Abstract Different directionally oriented sisal fibre reinforced epoxy resin composites have been prepared by compression moulding. The effect of temperature and frequency variation on dielectric constant ( e ′), dielectric dissipation factor (tan δ ) and on a.c. conductivity ( σ a.c. ) of the samples was measured. Measurements were in the temperature range 24–180 °C and in the frequency range 1–20 kHz. The sisal fibre epoxy composites were oriented parallel and perpendicular to the electric field. It was found that the dielectric constant, tan δ and a.c. conductivity increased with increasing temperature. The dependence of dielectric constant, tan δ and a.c. conductivity with frequency has also been studied and it was found that e ′ and tan δ of the epoxy and 0 and 90° oriented sisal fibre epoxy composites decreased with increasing frequency and a.c. conductivity increases with increasing frequency. Near the transition temperature of the epoxy the observed properties showed anomalous behaviour. Peaks for dielectric constant, tan δ and a.c. conductivity were observed. Clear relaxation peaks for tan δ around 169 °C were observed in epoxy resin, shifting to the lower temperature side with increasing frequency. The relaxation time of epoxy and 0 and 90° oriented sisal fibre epoxy composites has been calculated and it was found that τ ( s ) was 4.09×10 −5 , 5.52×10 −5 and 5.47×10 −5 , respectively at 100 °C. Semi log plots show that e ′ T / e ′ P tan δ T /tan δ P and σ a.c.T / σ a.c.P can be represented as follows e ′ T / e ′ P = k log f + c , tan δ T / tan δ P = a log f + b and, σ a . c . T / σ a . c . P = l log f + m