Improving plywood performances through hybridisation with plant fibres composites: a comparative analysis of quasi-static properties, failure kinetics and fatigue behaviour

Abstract This study explores the hybridisation of wood veneers with plant fibre-reinforced thermoplastic composites. Beech and Douglas fir plywood are made using environmentally friendly adhesives, polylactic acid (PLA) and recycled maleic anhydride-grafted polypropylene (rMAPP). Hybridised plywood is produced by incorporating flax fibres at specific locations within the lay-up. The mechanical performances of these hybrid laminates are assessed through 3-point bending tests. The results show that hybridisation enhances bending modulus and strength in nearly all tested configurations: the bending modulus increased by up to 24% in beech and 31 in Douglas fir, whereas bending strength gains reached up to 27 and 79%, respectively. Predictions based on classical laminate theory align closely with experimental data, validating its use for estimating the elastic properties of hybrid laminates. Additionally, the failure kinetics reveal that hybridisation enables stress redistribution within the composite layers, leading to improved bending strength even when outer veneers are damaged. A fatigue study under cyclic bending loads further demonstrates that hybridisation can double the fatigue strength of Douglas fir plywood over 1 million cycles compared to its non-hybrid counterpart. These findings highlight the potential of hybrid laminates to improve the mechanical performance and durability of wood-based composites for structural applications. Graphical abstract