This study investigates the interface between hemp fibre and thermoplastic polymer matrices such as polypropylene (PP) and poly-acrylate (Elium®). The analysis was conducted using both traditional dynamic contact angle measurements with various probe liquids and a more novel approach involving inverse gas chromatography (IGC) with multiple gaseous probes. The goal was to predict fibre–matrix compatibility based on surface chemical characterisation. Both methods showed good correlation, with the dispersive surface energy of the natural fibres ranging between 33 and 39 mJ/m², and a significant basic component contributing to the overall polar surface energy. IGC proved more effective at distinguishing between the predominantly apolar PP and the more polar poly(methyl methacrylate) (PMMA) based Elium, with the predicted thermodynamic work of adhesion notably higher for hemp–Elium interfaces compared to hemp–PP. Micromechanical testing, combined with microscopic imaging, further supported the observation of improved intermolecular adhesion between the natural fibres and the Elium matrix.

This study focuses on interlayer hybridisation of flax with silk fibres and the resulting damage mechanisms controlled by the hybrid composite configuration, can lead to an improved balance between stiffness, strength and toughness/ductility. The results demonstrate that a sandwich design configuration with flax layers at the outside of the laminate exhibit the highest increase in (pseudo-)ductility compared to monolithic flax fibre composites. X-ray computed tomography (XCT) revealed that fragmentation and debonding of the flax fibre layers can be achieved by optimising the hybrid laminate configuration and the volume fraction ratio between the two fibres, explaining the increased toughness of the hybrid composites.