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UBC Theses and Dissertations
Bonding process and performance of structural bamboo-wood laminates Zhang, Jialin
Sustainable development of bamboo-wood composites requires a better understanding and optimization of bonding. This thesis investigates the bonding process and performance of structural bamboo-wood laminates. A polylamellate cell wall structure, low tissue porosity and permeability, and poor surface wettability all hamper bamboo bonding with most softwood adhesives. Adhesive modification must be optimized in conjunction with more efficient material utilization and processes. Understanding the bonding mechanism between wood/bamboo and adhesives is essential for the development of modified adhesives for advanced hybrid composite. Phenol formaldehyde (PF) resins with two different molecular weights (MW) were tested for bamboo-wood bonding. Optical microscopy was used to observe the penetration of resin into the surface of solid or veneered wood (Douglas fir) and milled or flattened bamboo (Moso). The results showed that on the bamboo substrate, high MW PF largely remained in the glueline and only entered the lumina of cut or damaged cells near the bondline. Low MW PF penetrated cell wall corners of Moso bamboo but not the uncut lumens. Undamaged lumens seem impermeable to PF resins. Results from dry and wet bond shear tests showed that applying low MW PF to the bamboo and high MW PF to the wood surface separately significantly improved the bonding performance. The work also evaluated PF mixed with extenders and fillers for bonding veneer-type hybrid wood-bamboo composites with different glue application rates. The mixed plywood PF was comparable in both dry and wet bond shear strength and wood failure to using pure PF even at the same glue application rate due to its good gap filling capability. The findings indicate that plywood resin with fillers is a viable, lower cost-effective adhesive for veneer-type wood-bamboo composites. In conclusion, hybrid bamboo-wood composites are promising cost-effective approaches for the engineered bamboo industry, leading to viable building products. Bond qualification standards for wet bond criteria of plywood will need to be modified and adapted to accommodate the different resins and materials used in wood-bamboo composites. Further modifications are required to produce a stronger adhesive than the bamboo outer wall tissue in order to improve wet shear fiber failure rates.
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Attribution-NonCommercial-NoDerivatives 4.0 International