Effects of bamboo nodes on mechanical properties of thin-type bamboo bundle laminated veneer lumber (BLVL): From anatomical structure to penetration mechanism

Abstract

As a lightweight and high-strength green structural material, thin-type bamboo bundle laminated veneer lumber (BLVL) has been widely used in construction and transportation. However, bamboo nodes are often discarded as mechanical weak links during production and preparation. For the dredged bamboo bundle fiber, a large number of discontinuous fibers are found at the node, which are not conducive to the mechanical strength of BLVL. But on the other hand, the loose structure of the bamboo node facilitates the penetration and curing of the phenolic resin, which improves the bonding and mechanical strength of BLVL. Therefore, the influence rule by what bamboo nodes affect the mechanical properties of thin-type BLVL remains unclear. In this study, the effects of bamboo nodes and their distribution positions on the mechanical properties of thin-type BLVL were studied, and the underlying mechanism was identified from the perspective of assembly and bond penetration theory. Our findings indicate that the existence of bamboo node improves the bending strength (150.78 ± 29.24 MPa) and fracture toughness (2.58 J/cm2) of thin-type BLVL, but it’s still a potential weak link during stretching because of the influence of broken fibers. Considering that the tensile strength of thin-type BLVL exceeds practical standards, we suggest retaining bamboo nodes during production and processing, and the bamboo nodes should also be evenly distributed as far as possible during billet formation to maximize the use of bamboo without compromising its efficiency.