Mechanical properties of short flax fibre bundle/poly(ε-caprolactone) composites: Influence of matrix modification and fibre content

Composites were prepared by mixing biodegradable poly(ε-caprolactone) thermoplastic (PCL) with short flax fibre bundles. In order to improve fibre/matrix adhesion, poly(ε-caprolactone)-g-maleic anhydride copolymer (PCL-g-MA) compatibilizer was prepared in an internal mixer. The grafting reaction of maleic anhydride (MA) onto PCL polymer was carried out in presence of dicumyl peroxide as initiator. Mechanical properties were analysed as a function of compatibilizer concentration and fibre amount. In addition, thermal properties of flax/PCL and flax/PCL-g-MA composites were also examined by thermogravimetric (TG) analysis. Composites fabricated with flax fibre bundles and PCL-g-MA matrix showed the highest tensile and flexural strength. Scanning electron microscopy (SEM) of fractured surfaces confirmed the adhesion improvement between flax fibre bundles and PCL-g-MA matrix. Results obtained by thermogravimetric analysis showed that fibre addition and matrix modification slightly reduced the thermal stability of composites. The correlation between the experimental mechanical properties of short flax fibre bundle reinforced PCL composites with values calculated by various empirical models has also been analysed. For composites based on PCL-g-MA matrix, a good agreement was found between empirical model and experimental values for all fibre contents. However, for composites based on PCL matrix a good agreement only existed until 20 wt% flax fibre content, and beyond this value, experimental strength felt well below predictions.