Laminated solutions and grades of flattened bamboo-wood composite laminated veneer lumber

Bamboo, as a fast-growing material with high strength and stiffness, has attracted increasing attention for the manufacture of engineered composite products such as laminated veneer lumber (LVL). Bamboo-wood composite LVL (BLVL) has been developed to capitalize on bamboo higher mechanical performance and wood lower density to reduce product weight and facilitate bonding. However, performance instability and lack of grading standards limit application of BLVL in both structural and non-structural fields. Structure design, properties, and grades of flattened bamboo-poplar composite LVLs were investigated in this study. By considering different bamboo-wood volume ratios, different grades of flattened bamboo boards, and different composite structures, a total of 19 laminated structures were designed, manufactured, and experimentally evaluated. The properties of the BLVLs, including modulus of elasticity (MOE), modulus of rupture (MOR), interlaminar shear strength (ILSS), compression strength and immersion performance of adhesive bond, were systematically assessed. The results indicate that most of the tested laminated structures of BLVLs met 90E to 130E MOE grades (9–13Gpa) specified in the standard for LVLs (GB/T 20241–2021 and JAS0701–2023). With an increase in the MOE grade of flattened bamboo boards, the mechanical properties of BLVLs, MOE under both loading directions, MOR under edgewise bending, ILSS, and compression strength perpendicular to grain all gradually increased. As increasing bamboo ratio in BLVL increased, the MOE and MOR did not increase significantly while ILSS and compression strength perpendicular to grain increased progressively. Based on these findings, a series of recommended BLVL laminated structures were proposed for different MOE grades.