Properties of rotary peeled veneer and laminated veneer lumber (LVL) from New Zealand grown Eucalyptus globoidea

Abstract

Background: Eucalyptus species can be alternative plantation species to Pinus radiata D.Don (radiata pine) for New Zealand. One promising high value use for eucalypts is laminated veneer lumber (LVL) due to their fast growth and high stiffness. This study investigated the suitability of Eucalyptus globoidea Blakely for veneer and LVL production. Methods: Twenty-six logs were recovered from nine 30-year-old E. globoidea trees. Growth-strain was measured using the CIRAD method for each log before they were peeled into veneers. Veneer recovery, veneer splitting and wood properties were evaluated and correlated with growth-strain. Laminated veneer lumber (LVL) panels were made from eucalypt veneers only or mixed with radiata pine veneers to investigate the bonding performance of E. globoidea. Results: Veneers with no, or limited, defects can be obtained from E. globoidea. Veneer recovery (54.5%) correlated with growth-strain and was highly variable between logs ranging from 23.6% to 74.5%. Average splitting length in a veneer sheet was 3.01 m. There was a moderate positive association between splitting length and growth-strain (r = 0. 73), but no significant association with wood stiffness (r = 0.27). Bond quality of LVL panels prepared using E. globoidea veneer and a phenol formaldehyde adhesive did not satisfy AS/NZ 2098.2. Conclusion: Usable veneers for structural products could be obtained from E. globoidea at yields of up to 74.5%, but variation in the existing resource (which has not been genetically improved) was large. In particular, growth-strain reduced veneer recovery by splitting, largely independent of stiffness. The considerable variation in growth-strain and stiffness indicated a possibility for genetic improvement. Furthermore, a technical solution to improve bonding of E. globoidea veneers needs to be developed.

Engineering Wood Products from Eucalyptus spp.

“…e mechanical properties of E. grandis LVL were superior to those of poplar LVL, owing to the higher density of the E. grandis veneers. Meanwhile, E. globoidea was utilised to make LVL by Guo and Altaner [75]. Unfortunately, despite the high quality and good drying properties of the veneers acquired, the bond performance of the LVL produced is inadequate and does not fulfill e New Zealand standards.…”

“…Only 20% of useable veneers from E. grandis were recovered after severe end-splitting, according to Margadant [99]. Unfortunately, no technological solution to this problem has yet been discovered [75]. Apart from faults produced by growth pressures, another issue that needs to be handled is collapse and Eucalyptus lumber is difficult to dry due to its limited permeability and the presence of tyloses in the heartwood [100].…”

Genetic variation in wood properties of mid-rotation age Eucalyptus globoidea

“…Moreover, Keywords: Acoustic velocity; collapse; extractives; genetic gain; heartwood; natural durability; tree breeding; white stringybark value alternative not only to copper chromium arsenic (CCA) treated radiata pine, which is difficult to dispose of (Love 2007;Townsend & Solo-Gabriele 2006) but also naturally durable timber imports, which often originate from endangered or unsustainably harvested tropical sources (UNEP 2012). Envisaged uses for E. globoidea timber are primarily posts for the agricultural sectors but it can also be used for producing stiff veneers for laminated veneer lumber (LVL) (Guo & Altaner 2018) and sawn timber (Jones et al 2010). For the latter, stiffness and drying without collapse are relevant wood properties (Bootle 2005;Poynton 1979;Somerville & Gatenby 1996).…”