Robert L. McGavin

Mechanical Properties of Rotary Veneers Recovered from Early to Midrotation Subtropical-Hardwood Plantation Logs for Veneer-Based Composite Applications

AbstractThis paper experimentally investigates the mechanical properties of rotary veneers peeled from small-diameter hardwood plantation logs, recovered from early to midrotation subtropical hardw...

Influence of site, storage and steaming on Eucalyptus nitens log-end splitting

Key messageLog-end splitting is one of the single most important defects in veneer logs. We show that log-end splitting in the temperate plantation speciesEucalyptus nitensvaries across sites and within-tree log position and increases with time in storage.ContextLog-end splitting is one of the single most important defects in veneer logs because it can substantially reduce the recovery of veneer sheets. Eucalyptus nitens can develop log-end splits, but factors affecting log-end splitting in this species are not well understood.AimsThe present study aims to describe the effect of log storage and steaming on the development of log-end splitting in logs from different plantations and log positions within the tree.MethodsThe study was conducted on upper and lower logs from each of 41 trees from three 20–22-year-old Tasmanian E. nitens plantations. Log-end splitting was assessed immediately after felling, after transport and storage in a log-yard, and just before peeling. A pre-peeling steam treatment was applied to half the logs.ResultsSite had a significant effect on splitting, and upper logs split more than lower logs with storage. Splitting increased with tree diameter breast height (DBH), but this relationship varied with site. The most rapidly growing site had more splitting even after accounting for DBH. No significant effect of steaming was detected.ConclusionLog-end splitting varied across sites and within-tree log position and increased with time in storage.

Perpendicular to grain and shear mechanical properties of veneer-based elements glued from single veneer sheets recovered from three species of juvenile subtropical hardwood plantation logs

This paper quantifies the mechanical properties perpendicular to the grain and in shear of glued rotary peeled veneers, as would be encountered in veneer-based structural products (i.e. by including both the effects of hot pressing the veneers and the glue used during the manufacturing process), of three species recovered from juvenile (early to mid-rotation) subtropical hardwood plantation logs. This underutilised resource has currently little to no commercial value in Australia but proven potential to produce attractive veneer-based structural products. Determining these unknown properties is important as they constitute essential input data to ultimately predict the behaviour and design properties of veneer-based structural products in cost-effective numerical simulations. Two species planted for solid timber end-products (Gympie messmate—Eucalyptus cloeziana and spotted gum—Corymbia citriodora) and one species traditionally grown for pulpwood (southern blue gum—Eucalyptus globulus) are considered in the paper. The dynamic modulus of elasticity, compressive and tensile strengths perpendicular to the grain of veneer-based elements, each manufactured from single veneer sheets, were experimentally measured and are analysed herein. These properties are found to have no to weak correlation to the parent veneer sheet dynamic modulus of elasticity parallel to the grain, a value which is commonly measured in line to grade veneers. The shear modulus (in the longitudinal-tangential plane), also referred to as “modulus of rigidity”, through-the-thickness and rolling shear strengths were also experimentally measured, and the results are discussed in the paper. Little to no correlation to the veneer sheet dynamic modulus of elasticity parallel to the grain was found for these properties. Weibull distributions are fitted to all test results and presented to probabilistically consider the investigated properties in numerical simulations of veneer-based structural products.