title: Development of High-Value Engineered Wood Products Manufactured by Mixing Suboptimal-Quality Forest Resources
Creators: name: Nguyen, Hoan Hai
Publisher: name: Griffith University
Year: 2019
Subjects: subject: feasibility
subject: blending veneers
subject: suboptimal-quality
subject: native forest logs
subject: high-performance engineered wood products

description: In Australia, a significant amount of suboptimal-quality native forest resources (e.g., short length or small diameter logs of low value) have resulted from the sustainable management of native Australian forests and the processing sector. These resources, despite possessing high mechanical properties and often high durability, are not converted into value-added products due to size, technical and economic constraints. Additionally, a large amount of processed plantation-grown softwood is sold for low profit because it does not meet target product requirements despite being processed with an efficient system. To maximise Australia’s available forest resources and capitalise on their positive attributes, it is necessary to investigate the potential to blend these resources into an innovative, high-value engineered wood product. A potential commercialisation opportunity for the small volume of rotary veneers sourced from native forest logs is blending them with available plantation-grown softwood veneers to produce veneer-based products. This study aims to investigate the technical feasibility of blending veneers recovered from suboptimal-quality native forest logs of different species, with veneers from commercial softwood plantation logs to manufacture high-performance engineered wood products suitable for structural applications, namely beams. In the first stage, to understand the mechanical properties of veneer that can be recovered from select species, two native forest species (spotted gum [Corymbia] [SPG] and white cypress pine [Callitris glaucophylla] [CYP]) and one plantation-grown species (hoop pine [Araucaria cunninghamii] [HP]) were investigated. In total, 60 SPG logs, 60 CYP logs and eight HP logs were rotary peeled, providing the veneer feedstock for the sample manufacture. The native wood veneers were visually graded according to Australian and New Zealand standards. The dynamic modulus of elasticity (MOE) and density of each veneer were determined and plotted for all species according to the best fit Weibull distributions. In the second stage, a total of 18 panels of 15-ply laminated veneer lumber (LVL) were manufactured using six construction strategies influenced by best industry practice and knowledge to develop the concept of mixed-species veneer-based products. This process ascertained that LVL products can be manufactured from the three species examined and that blending species within a construction strategy can provide opportunities to maximise use of various forest resources. The mixed-species LVL demonstrated generally superior mechanical properties (bending, tension, bearing and longitudinal-tangential shear strength) to the reference single-species HP. In the third stage, a methodology was developed based on the genetic algorithm (GA) to optimise the manufacturing strategy for structural cross-banded laminated veneer lumbers (LVL-C) manufactured by mixing species. It aimed to minimise the cost of a family of LVL and LVL-C products by maximising the use of low-grade native wood veneers while targeting different stiffness and embedment strengths. The methodology was first developed using SPG and southern pine [SP] species. Accuracy of the approach was then verified using SPG and HP species. The developed algorithm consistently converged to similar solutions for all investigated cases, demonstrating its robustness. Finally, the obtained optimum construction strategies were validated against experimental results. In the final stage, a total of 12 panels manufactured from two different construction strategies for both the reference 12-ply LVL and optimised 12-ply LVL-C were examined. SPG and HP veneer were used to manufacture these panels. Minor correlation was identified between visual grading and dynamic MOE-based grading, suggesting that visual grading may not be the most appropriate method for manufacturing veneer-based products with targeted MOEs from native forest SPG veneers. Mixed-species LVL-C manufactured from native forest SPG and plantation HP veneers demonstrated mechanical properties higher than those readily commercially available LVL-C. This utilisation approach could represent a market opportunity for the veneers produced from under-utilised and under-valued native forest resources.