Renewable
structural materials derived from natural biological
materials can potentially replace non-renewable synthetic materials
for civil engineering and transportation applications. Here, inspired
by the functional gradient structure of bamboo, we propose a simple
and efficient two-step preparation strategy to convert natural bamboo
into a lightweight, high-strength, damping, and sound-insulating structural
engineering material called densified bundle-laminated veneer lumber
(DBLVL). DBLVL was prepared by finely grading and thinning three layers
of bamboo slices and removing the lignin and hemicelluloses from the
surface of bamboo bundles. This was followed by penetrating the phenol
formaldehyde resin and then solidifying and densifying it in situ.
DBLVL had superior mechanical properties due to its bamboo-like gradient
laminated structure, three-dimensional network distribution of adhesive
under high temperature and high pressure, in situ curing, and solid
interfacial bonding. It had a specific tensile strength of 297 MPa
cm3 g–1, which was superior to those
of many other construction materials. The tensile strength of DBLVL
reached 363 MPa, and the bending strength reached 219 MPa, which were
97.28 and 92.11% higher than those of natural bamboo, respectively.
The impact toughness reached 15.4 J/cm2. DBLVL also showed
excellent damping and vibration reduction (the first three damping
ratios were 2.35, 1.81, and 2.40%) and dimensional stability (the
thickness expansion rate after 24 h of water absorption was 4.43%).
Because of its excellent mechanical properties and hygrothermal stability,
DBLVL is expected to replace non-renewable synthetic materials as
a green and sustainable structural material for engineering applications.
The objective of this study was to design and develop a novel type of modular bamboo-composite wall using bamboo bundle veneer/wood veneer laminated composite (BLVL) with excellent physical and mechanical properties. The physical and mechanical properties of the important component of the bamboo-composite wall, BLVL, were characterized and the thermal insulation properties of three types of walls composed of different thickness of structural layers were studied. The results showed that the physical-mechanical properties of BLVL-composite walls were excellent. For BLVL wall panels, parallel and perpendicular to the glue layer, the static bending strength and elastic modulus were 137.8 MPa and 124.1 MPa vs. 1.37 GPa and 1.06 GPa, respectively. The internal bonding performance of BLVL was 3.07 MPa, 3 times greater than the standard requirement. The total heat transfer coefficients for models І and II of the bamboo-composite walls were 0.46 and 0.43 W/(m2·K), respectively, in line with the requirements of the “Public Building Energy Efficiency Design Standards” GB/T 50189-2005. The development of novel bamboo composite wall and its promotion and application in fabricated buildings have important market prospects and ecological and social values.
The objective of this study was to investigate the hygroscopic characteristics of three typical bamboo engineering composites (Bamboo scrimber (BS), bamboo bundle/wood laminated veneer lumber (BLVL), and bamboo laminated timber (BLT)) as well as predict their performance changes and service life in hot humid environments. The composites were subjected to three treatment conditions (23 °C, 63 °C, and 100 °C) for this experiment. The hygroscopic thickness swelling model and Fick’s second law were used to quantify the characterization and prediction of the water absorption, thickness swelling rate, and water absorption rate of BS, BLVL, and BLT. The results indicated that the order of the hygroscopic thickness swelling coefficient KSR and the diffusion coefficient D was BLT > BLVL > BS (at 23 °C and 63 °C). The optimal dimensional stability was displayed by BS, followed by BLVL and BLT. In addition to the hygroscopic properties, elastic modulus degradation was investigated. It was observed that the elastic modulus (MOR) degradation had a linear relationship with the aging temperature. After 152 h of the hydrothermal aging test (63 °C), the MOE of BS, BLVL, and BLT degraded by 44.33%, 53.89%, and 25.83%, respectively.
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