Development of High-Value Engineered Wood Products Manufactured by Mixing Suboptimal-Quality Forest Resources Author Nguyen, Hoan Hai Published 2019-12-20 Thesis Type Thesis (PhD Doctorate) School School of Eng & Built Env DOI https://doi.org/10.25904/1912/2400 Copyright Statement The author owns the copyright in this thesis, unless stated otherwise. Downloaded from http://hdl.handle.net/10072/390032 Griffith Research Online https://research-repository.griffith.edu.au Development of High-Value Engineered Wood Products Manufactured by Mixing Suboptimal-Quality Forest Resources HOAN HAI NGUYEN B.Eng., M.Sc. School of Engineering and Built Environment Griffith University Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy July 2019 1 Abstract 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 2 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 3 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. 4 Statement of Originality This work has not previously been submitted for a degree or diploma in any university. To the best of my knowledge and belief, the thesis contains no material previously published or written by another person except where due reference is made in the thesis itself. Signed: __________________ Date:10/7/2019 Hoan Hai Nguyen Griffith University 5 Acknowledgement of published Papers Section 9.1 of the Griffith University Code for the Responsible Conduct of Research (“Criteria for Authorship”), in accordance with Section 5 of the Australian Code for the Responsible Conduct of Research, states: To be named as an author, a researcher must have made a substantial scholarly contribution to the creative or scholarly work that constitutes the research output, and be able to take public responsibility for at least that part of the work they contributed. Attribution of authorship depends to some extent on the discipline and publisher policies, but in all cases, authorship must be based on substantial contributions in a combination of one or more of: • conception and design of the research project • analysis and interpretation of research data • drafting or making significant parts of the creative or scholarly work or critically revising it so as to contribute significantly to the final output. Section 9.3 of the Griffith University Code (“Responsibilities of Researchers”), in accordance with Section 5 of the Australian Code, states: Researchers are expected to: • Offer authorship to all people, including research trainees, who meet the criteria for authorship listed above, but only those people. • accept or decline offers of authorship promptly in writing. • Include in the list of authors only those who have accepted authorship • Appoint one author to be the executive author to record authorship and manage correspondence about the work with the publisher and other interested parties. • Acknowledge all those who have contributed to the research, facilities or materials but who do not qualify as authors, such as research assistants, technical staff, and advisors on cultural or community knowledge. Obtain written consent to name individuals. 6 Included in this thesis are papers in Chapters 3, 4, 5 and 6 which are co-authored with other researchers. My contribution to each co-authored paper is outlined at the front of the relevant chapter. The bibliographic details and status for these papers are: Chapter 3: McGavin R, Nguyen H.H, Gilbert BP, Tony Dakin, Adam Faircloth. (2019). A comparative study on mechanical properties of laminated veneer lumber (LVL) produced from blending various wood veneer, Bioresources, 14(4), 9064-9081. Chapter 4: Nguyen H.H, Gilbert BP, McGavin R, Bailleres H (2018). Optimisation of cross-banded Laminated Veneer Lumber manufactured from spotted gum and southern pine veneers, European Journal of wood and wood products, DOI: 10.1007/s00107-019-01434-7. Chapter 5: Nguyen H.H, Gilbert BP, McGavin R, Bailleres H (2019). Key mechanical properties of cross-banded laminated veneer lumber (LVL-C) produced from blending spotted gum and hoop pine, Bioresources, 14(4), 9117-9131. Chapter 6: Nguyen H.H, Gilbert BP, McGavin R, Bailleres H, Karampour H (2019). Embedment strength of mixed-species laminated veneer lumbers and cross-banded laminated veneer lumbers, European Journal of wood and wood products, (Submitted May 2019, under review). Appropriate acknowledgements of those who contributed to the research but did not qualify as authors are included in each paper. (Signed) _________________________________ (Date)____10/7/2019 PhD Candidate: Hoan Hai Nguyen (Countersigned) ___________________________ (Date)____10/7/2019 Principle supervisor: Associate Professor Benoit P. Gilbert (Countersigned) ___________________________ (Date)_____10/7/2019 External supervisor: Dr. Robbie R. McGavin 7 List of Publications Journal papers: Nguyen H.H, Gilbert BP, McGavin R, Bailleres H (2018). Optimisation of cross-banded Laminated Veneer Lumber manufactured from spotted gum and southern pine veneers, European Journal of wood and wood products, 77(5), 783 – 797. McGavin R, Nguyen H.H, Gilbert BP, Tony Dakin, Adam Faircloth. (2019). A comparative study on mechanical properties of laminated veneer lumber (LVL) produced from blending various wood veneer, Bioresources, 14(4), 9064-9081. Nguyen H.H, Gilbert BP, McGavin R, Bailleres H (2019). Key mechanical properties of optinum cross-banded laminated veneer lumber (LVL-C) produced