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

Abstract

This paper experimentally investigates the mechanical properties of rotary veneers peeled from small-diameter hardwood plantation logs, recovered from early to mid-rotation subtropical hardwood plantations. The study aims at providing essential probabilistic data needed to ultimately predict the capacity and reliability of veneered based composites structural products (such as LVL and plywood) from characteristics which can be measured in line during manufacturing. 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) were studied. The compressive and tensile Modulus of Rupture (MOR) of the veneers, parallel to the grain and for veneer based composite applications, were experimentally investigated. Results show that the compressive MOR for all species typically ranges from 30-50 MPa (for MOE < 12,000 MPa) to 60-90 MPa (for MOE > 22,000 MPa). The tensile MOR is typically lower than or in the range of the compressive MOR for MOE less than 12,000 MPa, while for larger MOE (MOE > 22,000 MPa), tensile MOR greater than 140 MPa were observed. The total knot area ratio (tKAR) of the veneers is also analysed and Weibull distributions were found to provide a good characterisation of the statistical repartition of the tKAR value along the length of a veneer sheet. For each species, equations to best predict a veneer MOR from its measured MOE and tKAR value are derived and fit the experimental results with a coefficient of determination between 0.63 and 0.74. The variability of the MOR of each species was accurately modelled by Weibull distributions, with the distribution parameters determined based on the experimental data. Results shown that southern blue gum and Gympie messmate is the most and least sensitive species to size effects.

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

“…• One 630 mm (along grain) × 100 mm sample and one 1,130 mm (along grain) × 150 mm sample for compression and tension parallel to the grain, with the results reported in Gilbert, et al (2017a).…”

“…While all 90 × 3-ply LVL per species were used in Gilbert, et al (2017a) to determine the mechanical properties parallel to the grain, only 45 × 3-ply LVL per species were selected in this study to assess the perpendicular to grain and shear properties of the veneers. 45 samples per species were deemed a reasonable number to capture the variability in each investigated mechanical property while preparing for and performing a realistic number of tests.…”

“…The approach above is currently followed (Gilbert 2018, Gilbert, et al 2017a, Gilbert, et al 2017b to determine the mechanical properties of Laminated Veneer Lumber (LVL) and plywood panels manufactured from Australia's underutilised hardwood plantation forest resources in structural applications, namely juvenile (early to mid-rotation) hardwood plantation logs. The methodology will also be extended to derive the design properties of innovative veneer-based hollow structural products manufactured from the same resource (Gilbert, et al 2014, Gilbert, et al 2017c.…”

“…While the tensile and compressive strengths parallel to the grain of glued rotary peeled veneers recovered from three species of the above juvenile hardwood logs have been quantified in Gilbert, et al (2017a), their mechanical properties perpendicular to the grain and in shear still need to be investigated. Two of these species were planted for solid timber end-products (Gympie messmate (GMS -Eucalyptus cloeziana), spotted gum (SPG -Corymbia citriodora)) and one species for pulpwood (southern blue gum (SBG -Eucalyptus globulus)).…”

Paineis híbridos de lâminas e partículas de madeira para uso estrutural

“…Dentre os painéis engenheirados à base de madeira, destacam-se os painéis compensados, oriented strand board (OSB) e medium density particleboard (MDP), servindo como alternativa ao uso de madeira serrada na construção civil e rural, móveis, entre outras (BERTOLINI et al, 2014;FERRO et al, 2015;CHIROMITO et al, 2016;NASCIMENTO et al, 2016;GILBERT et al, 2017).…”