Experimental study and FE analysis of laminated bamboo–timber composite beams subjected to bending perpendicular to lamination

Laminated bamboo–timber composite beams offer a sustainable, high-performance alternative for structural applications. This study investigates the flexural behavior of five-layer bamboo scrimber–Douglas fir composite beams subjected to four-point bending perpendicular to the lamination plane. Experiments showed that failure was governed by tensile rupture of the bottom bamboo fibers, while adhesive interfaces remained intact. Compared with pure timber beams, the composites achieved increases of 108.1% in ultimate load and 21.9% in flexural stiffness. A nonlinear finite element (FE) model incorporating elastoplastic constitutive laws was developed and validated against the test results, with discrepancies in stiffness and ultimate load generally below 10%. Parametric analyses revealed that elastic modulus variations predominantly affect initial stiffness, while ultimate capacity is controlled by bamboo tensile strain limits. The bamboo layer ratio strongly influences performance, with optimal efficiency at ratios of 0.6–0.8. Positioning bamboo at the outermost layers maximizes stiffness, and increasing beam height substantially enhances strength and stiffness following the classical bending law. The findings provide guidance for optimized design of bamboo–timber composite beams in sustainable construction.