Huanrong Liu

Natural arc-shaped bamboo laminated lumber (ABLL) represents an eco-friendly advanced material. This study introduces an innovative preparation method and manufacturing process to enhance production efficiency and reduce costs. Full-scale processing experiments were conducted to evaluate the feasibility and performance of the innovative integrated fixed-arc and drying process. Bonding integrity was assessed through glue-line shear strength and soak-delamination resistance. The maximum dry glue-line shear strength and delamination length achieved were 8.19 MPa (>traditional value of 3.5 MPa) and 21.8 mm (<traditional value of 25 mm), respectively. Comparative analysis of material utilization of eight-layer natural arc-shaped bamboo laminated lumber demonstrated a rate of 77.9% (<traditional value of 60%). This optimized process significantly contributes to elevated production efficiency and material yield in natural arc-shaped laminated lumber manufacturing.

Natural arc-shaped bamboo laminated lumber (ABLL) is an engineering material made from recyclable and rapidly renewable bamboo. Objectives: to enhance processing mechanization by (i) establishing a fixed-arc dimensional model for bamboo splits, (ii) designing an integrated mold capable of simultaneous shaping and drying, and (iii) validating its performance through simulation and experiment. Methods: numerical modeling simulated the operational process, and physical tests measured split length, thickness, inner and outer chord lengths, and moisture content. Results: after the mold completes the arc-fixing and drying of bamboo splits, parameters including the splits’ length, chord length, thickness, and moisture content are suitable for subsequent processing. Based on simulation results, the working mechanism of load application and deformation of bamboo during the equipment’s arc-fixing process was analyzed. The cylindrical arc geometry causes uneven material deformation and stress distribution during arc-fixing. Arc-fixing of bamboo splits results in irreversible edge densification. Thus, gluing should be performed promptly to prevent warping. Evaluation metrics for arc length data—including RE ≤ 8.46%, R² ≥ 0.71, and RMSE ≤ 3.61—confirm the reliability of the dimensional model and virtual prototype simulation model. The proposed method was expected to provide a reference for the development of devices specifically designed for ABLL.

As a natural biomass material, bamboo is subject to variations in culm size as well as in physical and mechanical properties that substantially influence processing and product quality. The diameter, thickness, and hardness of bamboo culms are critical factors for the output and quality of flattened bamboo board (FBB). In this study, the effects of different hardness modulus (HM) grades on the physical and mechanical properties of FBB were examined. The results showed that the HM of Moso bamboo (Phyllostachys pubescens) followed a normal distribution. Nine grades of HM could be divided by an interval of 5 KN/mm². The physical and mechanical properties of FBB were positively correlated with the HM of bamboo culms. Compressive strength, tensile strength, and shear strength, as well as the bending properties of FBB, each increased with increasing HM. Furthermore, under the same conditions, the mechanical properties of FBB were superior to those of both bamboo strips and bamboo culms. The softening, flattening, and planing processes were beneficial in improving the performance of bamboo. The strong correlation between HM and the properties of FBB indicates that the HM grading of bamboo culms can be used in bamboo processing to produce high-quality FBB products with uniform performance.

Bamboo is a natural material widely used in buildings and bridges that has good mechanical properties. However, the longitudinal connection of bamboo culms is a major problem for the bamboo industry. In this study, sleeve-nailed bamboo specimens were produced, which contained three bamboo pieces. Two bamboo pieces with similar diameters were longitudinally joined by inserting a short bamboo culm with a smaller diameter, fixed with nails. The flexural performance of single beams and two-culm beams were studied. The load-displacement curves and fracture behavior of the specimens were investigated. The results show that the flexural bearing capacity of the single connected bamboo specimen was relatively smaller than that of an unconnected one, while the flexural bearing capacity of the two-culm beam was improved significantly. It can be seen that the lateral connection of bamboo specimens can improve the bearing capacity of the combined bamboo culms. This study provides a basis for promoting the application of sleeve-type nailed connections for bamboo.

Due to the low specific strength of bamboo oriented strand boards compared with the commonly used wooden building materials, reasonable and novel cross-section designs of bamboo columns fabricated from bamboo oriented strand boards as structural members were investigated. An axial compression experiment was carried out on full-scale bamboo columns to characterize the ultimate behaviors under a concentric load. The ultimate bearing capacities of solid, hollow and five-core columns of the same height were not obviously different from each other. The columns with a larger slenderness ratio showed lower ultimate loads and higher axial deflections. The short columns experienced failure due to material crushing, and the long columns experienced a combination of material crushing and inelastic buckling. The empirical equations for predicting the ultimate bearing capacity for wooden columns showed applicability for bamboo columns. Non-linear finite element modeling analyses were carried out to validate the experimental results, and a satisfactory agreement was found in the failure modes and ultimate bearing capacity.

Bamboo is recognized as a potential and sustainable green material. The longitudinal-splitting and shear strengths of bamboo are weak but critical to its utilizations. To discuss the different shear performances of bamboo, the shear strength and behaviors of bamboo culm were investigated by four test methods: the tensile-shear, step-shear, cross-shear, and short-beam-shear methods. Then, the different shear performance and mechanisms were discussed. Results indicated that the shear strength was significantly different in the four test methods and was highest in the step-shear-test method but lowest in the tensile-shear-test method. Moreover, the typical load-displacement curves were different across the shear methods but were similar to the curves of the respective loading modes. The axially aligned fiber bundles played an important role in all the shear performances. In the tensile-shear method, specimens fractured at the interface of the bamboo-fiber bundles. However, compress-shear behaviors were a combination of compression and shear. Then, the cross-shear method, in compress-shear, was lower than that of the step-shear method because of oval-shaped bamboo culm sections of different thickness. In the short-beam shear method, the behaviors and shearing characteristics were like bending with the fiber bundle pulled out.

Bamboo hardness test standards are not available. The study aimed to develop a new method of testing bamboo indentation hardness. With the V-shaped prismatic head, bamboo rings with different lengths were tested. The V-shaped indentation coefficient (IC) was defined. The results showed that the IC had a good correlation with compression strength. The V-shaped IC increased with the increase in the longitudinal height of the bamboo pole, and the variance analysis showed significant differences in different axial directions of the same bamboo ring. In addition, the correlation between density and IC is good. The V-shaped IC can be applied in bamboo gra

The objective of this study was to investigate the impact performance of bamboo oriented strand board under different impact energy. Bamboo oriented strand board with two types of strand orientation distribution, both with mainly parallel aligned strand orientation (LVSL) and three-layer assembly with orthogonally oriented strands (BOSB), were prepared. The impact properties of the boards, both untreated and treated with submersion, were investigated at seven energy levels. Additionally, the damage morphology was characterized using an X-ray computed tomography (CT) scanner. The results indicated that BOSB provided a larger maximum load carrying capacity, and represented superior impact properties compared to LVSL. The shapes of force/energy–time history of BOSB and LVSL were different from projectile energy levels, and they were related to the specimen destruction forms via CT scanning. Moreover, CT scanning revealed that LVSL and BOSB exhibited similar damage behaviors, which mainly included delamination and fibers breakage. The dent depth of BOSB on the impact site was less than LVSL’s for touch types, and there was more internal fracture inside the layers of LVSL at relatively higher energy levels of 300 J and 450 J. Furthermore, BOSB still exhibited better impact performance than LVSL under the condition of submersion.