Yield behaviour of renewable biocomposites of dimer fatty acid-based polyamides with cellulose fibres

The yield behaviour of dimer acid-based polyamides (DAPA) and DAPA reinforced with cellulose fibres (CF) was examined in this study. Both dynamic mechanical analysis (DMA) and tensile tests were used to follow the effect of strain rate or frequency, temperature and filler content on the transitions temperatures, the storage modulus and the yield stresses. The DMA results show that the storage modulus increases with increasing CF concentration. The tensile tests reveal that the yield stress is strain rate, temperature and CF concentration sensitive. Both activation enthalpy and activation volume calculated by the Eyring’s model reveal a slight increase of activation energy with increasing filler content and a decrease of the activation volume. A micromechanically-model was used to predict the yield stress of both DAPA and DAPA/cellulose composites. The model predictions of the yield stress are in good agreement with the experimental data.