Interfacial characterisation of flax fibre-thermoplastic polymer composites by the pull-out test

The interface between flax fibres and thermoplastic polymer matrices has been investigated. Two types of flax fibres have been used: dew retted and upgraded Duralin fibres. The latter fibres have been treated by a novel treatment process for improved moisture and rot sensitivity. The apparent shear strength of dew-retted and upgraded Duralin fibres embedded in high and low density polyethylene, polypropylene and maleic anhydride modified polypropylene, respectively, has been calculated from the maximum force measured from the pull-out test using the Kelly-Tyson equation. Higher apparent shear strength values have been measured in the case of high density polyethylene. An improvement in the interfacial shear strength by the use of upgraded flax fibres has not been clearly observed. The curves of pull-out force versus displacement for all samples are typical of a brittle fracture mixed mode interface behaviour. The pull-out test of flax fibre-polymer matrices exhibit similar characteristics with the pull-out test of synthetic fibre-polymer systems.