Barbara Ozarska

A review of the utilisation of hardwoods for LVL

Abstract This review on the use of hardwoods for the production of LVL revealed that a large number of research studies have been carried out, particularly in North America and three Asian countries (Japan, Malaysia and China). However, the studies have been restricted to species of low to medium density, i.e. 290 to 693 kg/m3. Two major potential uses of hardwood LVL have been investigated in these studies: domestic and industrial structures, and various furniture components. The production of structural LVL in North America and Asia was based predominantly on low density hardwoods. A study currently carried out in Europe aims at using medium density hardwoods for structural LVL. The LVL used for furniture components was produced from medium density hardwoods. No work has been undertaken outside Australia on the use of high density species for LVL. In Australia, studies undertaken on the production of LVL and hardwood plywood from eucalypts revealed that there were significant problems in gluing the dense raw material which often had a high level of extractives. Peeling low quality, small diameter eucalypt logs also created problems when the traditional plywood processing techniques were used.

Forest and Plantation Development in Laos: History, Development and Impact for Rural Communities

SUMMARY This paper presents a historical review and overview of the Lao forest sector. Previous research and forestry related policy documents of Laos indicate that forest management has evolved through six stages. Initially, natural forests were used by local people for basic needs. Little was destroyed or degraded. The second stage was greatly influenced by French colonisation. The third was a period when natural forests made major contributions to national economic growth, when natural forests were increasingly and widely harvested. Remaining phases involved growing criticism of Lao forest management practices from international organisations and the Laos National Assembly. Recently, private investment in tree plantations has increased. Overall, ineffective policies and inefficient institutional agencies have seriously constrained Lao forest management. Policy instruments such as concessions to plantation development need to be modified and balanced by the promotion of outgrower schemes. Plantation investments should be encouraged to follow international standards, guidelines and codes of practice.

Design of a Microwave Chamber for the Purpose of Drying of Wood Components for Furniture

A specialized multiple-magnetron, microwave chamber was designed and built to facilitate research into the drying of bent timber components for furniture manufacture. This article reports on the design of this chamber and the findings from experimental drying of wood components. The microwave chamber provides three power levels (2, 4, and 6 kW) by engaging appropriate numbers of standard 1 kW microwave magnetrons. Preliminary experiments revealed that good drying quality was achieved when the microwave power level was set to 2 kW and cycled such that microwave power was applied to the chamber for 30 s, followed by a 90 s relaxation time during which no microwave power was applied and internal heat and moisture diffusion could alleviate hot spots inside the wood samples. The use of microwave drying reduced the drying time from weeks or months to hours. Straight components that started with a low moisture content and all bent components, irrespective of their initial moisture content, were dried with no evidence of drying degrade or collapse. However, the straight components that started with a high moisture content showed severe surface collapse. This may have been because these samples were taken from poor-quality material that was considered unsuitable for bending.

Temperature and moisture content behaviour in microwave heated wood prior to bending – Mountain Ash (Eucalyptus regnans)

AbstractThe Cooperative Research Centre for Wood Innovations, within the University of Melbourne, has developed an innovative wood bending technology which involves the use of microwave softening of wood prior to bending, an automated process of wood bending suitable for ‘‘mass production’’ and microwave drying of bent components. This paper discusses the microwave softening of wood required prior to bending, in particular, temperature and moisture distribution and transmission in cross-sections of microwave heated wood. Optimal heating parameters for softening wood using microwave irradiation were also investigated.

Assessment of Microwave Bending Capabilities for Australian Wood Species

An innovative wood bending technology has been developed by the University of Melbourne, within the Cooperative Research Centre for Wood Innovations, which involves the microwave softening of wood ...

Strain measurement of softened Eucalyptus regnans wood during bending operation using a low-cost single camera optical method

Abstract An important requirement for developing an understanding of wood bending mechanics is to determine the mechanical response of softened wood during bending. This involves experimentally measuring wood’s deformation or strain. Many wood bending studies have been conducted over the past 80 years to increase the understanding and investigate methods of ultimately improving the wood bending operation. The majority of these studies investigated the particular type of method of softening, using minimum bending radius and quality as a measured response. However, there is sparse literature in the public domain that offers a means of gaining an understanding of the mechanics of a wood specimen during a bending operation. This paper introduces a low-cost optical-based method for measuring engineering strain in softened wood. The method requires minimal specialised equipment and has been successfully used to determine the engineering strain response of Eucalyptus regnans during the bending process.

Wood bending mechanics: effect of resultant end-force

Abstract An innovative means of measuring the end-forces in a softened wood specimen during a bending process has been developed, incorporating a resultant end-force sensor. The impact of end-forces on wood deformation and associated bending performance has been investigated, and a correlation was found to exist between end-force and bending performance. The technique enables the systematic control of axial compression end-forces so that bending induced wood failure, as measured by longitudinal strain at the convex edge, can be minimised. While incorporating traditional manual end-force adjustment, it is envisaged that that this technique could facilitate automation of the bending process. Friction was identified as a significant impediment to the establishment of a reliable relationship between end-force and wood strain during bending.

Strength ratios of knots in bending for two Alaskan softwood species.

Most of the furniture manufactured in Australia is made from the eucalypt timber species. Although in the past old-growth eucalypt timbers were primarily used for the production of furniture and other appearance products, a global trend to promote the sustainable use of timber resources has stimulated the industry to adapt to the change by utilizing plantation and regrowth timbers. Reference materials on the properties of Australian species provide data on old-growth timbers but limited publications are available which compare the properties of plantation and old-growth timbers for high-value wood products. So, a research study was undertaken with the goal of investigating the suitability of seven plantation-grown Australian hardwoods for furniture (15 to 40 years of age of harvest). Selected properties of the timbers (density, modulus of elasticity [MOE], and modulus of rupture [MOR]) were assessed and compared with the data on old-growth timber of each species. The results of the study showed that the densities of young plantation timbers were not much lower than those of old-growth wood. The ratio of plantation to old-growth wood varied between 0.82 (for 18-year-old Corymbia maculata) and 0.99 (for 40-year-old Eucalyptus cladocalyx). The ratio of plantation to old-growth wood for MOE and MOR varied between the species as well as between the age of the trees. It was concluded that special care should be taken when using young plantation timbers for furniture production. Although 15-year-old timbers could be confidently used for non-structural appearance components of furniture, they should not be considered as reliable engineering material for structural components of furniture due to the high variability of their engineering properties.

Comparing two internal check measurement methods for wood drying quality assessment

Internal checks that are created in the interior of lumber during or after timber drying seriously affect the quality and value of timber used for the production of high value wood products. This study compared two different methods of assessing wood drying quality, by using either an image analysis ImageJ or Digital Calliper technique, to determine the percentage loss of cross section due to internal checking. The study revealed that there was a significant difference in the total area of internal checks, but the overall timber quality classes determined from both techniques were identical based on the Australian and New Zealand standard for timber quality assessment.

Assessing the potential of wood welding for Australian eucalypts and tropical species

The wood welding potential of Australian and tropical species has been investigated. Optimized parameters for Eucalyptus saligna, Eucalyptus pilularis, Corymbia maculata, Ochroma pyramidale, and Tectona grandis were determined using a standard tensile strength test. The results confirmed the importance of density in the optimisation process. The grain direction also proved to have a significant impact on the welded joint strength of species featuring large wood rays or vessels in diagonal and/or radial pattern. Wood welding could therefore be an alternative for such species where gluing is required.