Kate E. Semple

The suitability of five Western Australian mallee eucalypt species for wood–cement composites

Abstract There are currently around 10 000 ha of mallee eucalypt plantations in Western Australia that have been established primarily for the production of eucalypt leaf oils. Planting rates are projected to increase dramatically in future. The financial viability of these plantations is dependent upon finding a commercial outlet for the small diameter wood and bark residues, which may constitute up to half of the harvested material. The potential for such residues to be utilised in cement-bonded wood composite panels was investigated here. The woody residues of five species of mallee eucalypts, as expected, inhibited the hydration reaction of Portland cement, but not to such an extent as to make the wood unsuitable for cement composites. The bark of one of the species, E. loxophleba ssp. lissophloia, inhibited the setting of Portland cement to such an extent that the residue of this species (with bark present) was unsuitable for use in wood–cement composites. Three out of the five mallee eucalypt species retained relatively good compatibility with cement even when bark was present in the residues. The flexural properties (MOR and MOE) of cement-bonded panels manufactured from chipped mallee eucalypt residues were low in comparison to similar boards made from radiata pine, probably because of the smaller particle size and lower aspect ratio of the eucalypt wood residues. Boards made from E. polybractea, E. horistes and E. kochii ssp. plenissima were stronger and more resistant to water than those made from E. angustissima and E. loxophleba ssp. lissophloia. On the basis of our findings, opportunities and challenges for the commercial utilisation of mallee eucalypt wood for wood–cement composites are discussed.

Cement hydration tests using wood flour may not predict the suitability of Acacia mangium and Eucalyptus pellita for the manufacture of wood-wool cement boards

Summary Wood-wool cement boards (WWCBs) are manufactured in many tropical countries which have extensive eucalypt and acacia plantations. Wood from such plantations could act as a potential raw material for WWCBs, but the suitability of most tropical eucalypts and acacias for the manufacture of such products is unknown. This study was undertaken to assess whether the standard laboratory test for wood-cement compatibility, which measures heat of hydration in wood flour-cement mixtures, is an appropriate method for screening tropical eucalypts and acacias for their compatibility with cement and suitability for the manufacture of WWCBs. Wood samples from a tropical eucalypt (E. pellita) and a tropical acacia (A. mangium) were tested in two forms, i. e. flour and wool, for their compatibility (expressed by maximum hydration temperature and CA-factor) with Portland cement. Form significantly influenced the effect of the wood on cement hydration, resulting in a different species compatibility ranking for flour and wool. As the heartwood content of wood-wool-cement hydration test samples increased, Tmax. and CA factor increased whereas the opposite occured for those containing wood flour. Tests using wood flour ranked E. pellita as being more compatible with cement than A. mangium whereas the ranking was reversed when wood-wool was used. Furthermore at low wood levels the compatibility of samples containing wood-wool or wood flour with cement was similar whereas at high wood levels, samples containing wood-wool were much more compatible with cement than those containing wood flour. Laboratory tests designed to screen eucalypts and acacias for their compatibility with cement should use wood in a coarser form with a lower surface-to-volume ratio than flour. Caution should be exercised if using results from wood flour-cement hydration tests to estimate the suitability of wood species for the manufacture of WWCBs and possibly other wood-cement composites.

Evaluating the suitability of hybrid poplar clones for the manufacture of oriented strand boards

Abstract Clonal trees from five different plantation-grown, industrially relevant hybrid poplar genotypes of the same age, grown on a common site in British Columbia, Canada, were tested for their performance in strand production and properties of oriented strand board (OSB). The results were compared against a benchmark mill-run OSB furnish derived from native aspen (Populus tremuloides). Variation in solid wood density among the hybrid poplar clones was shown to influence the compaction ratio and densification of the OSB, which in turn led to variation in board strength properties. After accounting for specimen density using co-variate statistical models, it was apparent that there were significant effects of genotype on bonding strength and thickness swell. Lower density wood from the fastest growing P. deltoides×P. trichocarpa (DTAC 7) clone resulted in better mat compaction and higher bond strength, whereas higher density wood from a P. trichocarpa×P. deltoides (TD 50-184) clone resulted in lower compaction and bonding strength. Flexural strength (rupture and elastic moduli) and nail pull through were not as significantly affected by either board density or genotype when adjusted for density. The study clearly demonstrates that fast grown, large diameter wood of lower initial wood density from hybrid poplar is highly suited for OSB production.

Compatibility of 8 temperate Australian Eucalyptus species with Portland cement

Subject Few of the over 800 species of Eucalyptus have been screened for their compatibility with Portland cement and suitability for the manufacture of wood-cement composites. The compatibility with Portland cement of 8 temperate species of Eucalyptus native to SE Australia was measured, and the effects of sapwood content and of extractive removal on wood-cement compatibility were assessed.

Comparison of the flexural behavior of natural and thermo-hydro-mechanically densified Moso bamboo

The flexural properties in the longitudinal direction for natural and thermo-hydro-mechanically densified Moso bamboo (Phyllostachys pubescens Mazel) culm wall material are measured. The modulus of elasticity (MOE) and modulus of rupture (MOR) increase with densification, but at the same density, the natural material is stiffer and stronger than the densified material. This observation is primarily attributed to bamboo’s heterogeneous structure and the role of the parenchyma in densification. The MOE and MOR of both the natural and densified bamboo appear linearly related to density. Simple models are developed to predict the flexural properties of natural bamboo. The structure of the densified bamboo is modelled, assuming no densification of bamboo fibers, and the flexural properties of densified bamboo are then predicted using this structure and the same cell wall properties of that of the natural material modelling. The results are then compared with those for two analogous structural bamboo products: Moso bamboo glulam and scrimber.

Compatibility of some Australian acacias with Portland cement

The compatibility of the wood of several acacia species with Portland cement was measured and compared with that of spruce and larch.

Properties of Commercial Kraft Paper Honeycomb Furniture Stock Panels Conditioned under 65 and 95 Percent Relative Humidity

Abstract Physical and mechanical properties of a range of commercially produced kraft paper honeycomb stock panels were assessed to provide technical information of interest to primary and secondar...

Preliminary Experiments on the Manufacture of Hollow Core Composite Panels

Structural honeycomb panels consist of a lightweight, often paper, honeycomb column core between two thin, stiff face sheets, which results in a very light structure with high strength and stiffnes...

Edge Reinforcement of Honeycomb Sandwich Panels

Protection of the fragile honeycomb core material in hollow-core panels has long been a subject of interest for the manufacturers because it is necessary to seal the panel edges to prevent damage. Traditionally this has been accomplished by using edge banding, which has the added benefit of improving panel bending strength and stiffness. This study focuses on evaluating the effects of edge banding on the bending strength and stiffness properties of honeycomb core panels. The honeycomb panels were made with a combination of different face sheet materials (3-mm hardboard or 6-mm medium-density fiberboard [MDF]), rail types (particleboard or yellow poplar [Liriodendron tulipifera]), and rail widths (10 or 38 mm), and had edge-band materials fixed to their long edges using either direct coating, stabilizer edge, or surface folding techniques. Panels made with the 6-mm MDF face sheet and 38-mm poplar rails had the highest strength properties. To safely apply edge banding to honeycomb core panels, a solid edge ...