• Multi-scale analysis revealing a longitudinal gradient in structure and properties within banana leaf midrib. • Evidence of progressive fibre maturation (composition, crystallinity, thermo-mechanical behaviour). • Targeted fibre selection optimising the density-performance trade-off for bio-based biocomposites. Bundles of lignocellulosic fibres derived from the midribs of banana leaves ( Musa spp .), an abundant agricultural by-product in Cameroon, were characterised according to their longitudinal position (base, middle, apex). Extracted by water maceration, they were subjected to chemical, structural, hygroscopic, thermal and mechanical analyses. The results reveal a longitudinal gradient ranging from an amorphous structure, rich in lignin and highly hygroscopic at the base, to an ordered structure, dominated by cellulose and thermally stable at the apex. Tensile tests indicate that apical fibres exhibit higher strength, whilst basal fibres, which are less strong, display increased stiffness. This mechanical variability, linked in particular to differences in diameter, can be described by the Weibull model. The longitudinal sampling approach demonstrates that the midrib constitutes a structured resource enabling the targeted selection of fibres according to specific applications. This strategy reduces intrinsic variability and improves the density-performance trade-off. Apical fibres appear particularly suited to lightweight biocomposites, whilst basal fibres are suitable for less demanding applications.
Omgba et al. (Fri,) studied this question.