Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Rotary friction welding produces joints by inserting wood dowels, with a specific rotation and feed rate, into pre-drilled holes made in wood substrates. Studies on the welding of fast-growing eucalypts from Brazilian planted forests are recent. Therefore, this research aimed to evaluate the macro and microstructural and thermochemical changes at the dowel/substrate interface of eucalypts welded joints from Brazilian planted forests and to determine the mechanical strength of two-piece eucalypts welded joints. Specimens formed by eucalypts dowels and substrates were produced. Subsequently, visual evaluation and scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric, differential scanning calorimetry and tensile tests were performed. The results reveal that the rotary friction welding parameters adopted contribute to the densification of the welded interface and the formation of a structure responsible for joining the dowel and the substrate, providing mechanical strength to the joint. The cellulose crystallinity index and the apparent crystallite size of the eucalypts welded sample increase due to thermal degradation of amorphous components. The rupture of the welded joints is ductile and their average strength is 2,1 MPa. Welded joints of fast-growing eucalypts, from Brazilian planted forests, are suitable when the rotary friction welding parameters are similar to those used for eucalypts woods from Australian forests.

In the Amazonian forests of Perú a large variety of native wood species can be found, of which only a few are commercially exploited. Exploitation is focused on high density durable hardwoods for flooring applications. After selective logging of a few valuable trees the forests often are considered being “unproductive” because there is no market for most of the remaining trees. Having a long-term sustainable forest management and utilization plan in mind, a continuous extraction of more tree species is desirable. For opening out new markets for lesser-used species a concise knowledge of their physical and mechanical properties is essential. Fifteen lesser-used Peruvian wood species were investigated to characterize their wood/water relations. Density, shrinkage behavior, and sorption characteristics were determined. In addition, the functional relation between electrical resistance and moisture content was determined to provide a sound basis for non-destructive moisture content measurements.

Plywood is used for insulation systems in liquid natural gas cargo ships because of its good thermal properties. However, there are only a few research investigating the mechanical properties of plywood exposed to ultra-low temperatures. This study aims to determine how plywood reacts when exposed to ultra-low temperatures, such as - 196 °C. To achieve this purpose, the present study investigated the bending strength, modulus of elasticity, and tensile-shear strength of painted and film-coated plywood under ultra-low temperatures. The mechanical properties of plywood were discovered to be significantly impacted by the ultra-low temperature as a result of this research.. Moreover, not only the bending strength of the painted and film-coated plywood increased with decreasing temperature, but also the modules of elasticity of the painted and film-coated plywood increased. At decreasing temperature, the tensile shear strength of the painted and film-coated oven-dried plywood increased, but the ensile-shear strength of painted and film-coated air-dried plywood decreased. The tensile shear strength of air-dried plywood was determined to be more sensitive to the temperature change. Therefore, attention should be paid to plywood used in liquefied natural gas cargo ships with high humidity.

onservation of historic timber structures is of great importance for cultural inheritance and community identity promotion. However, most of the current methods available for ancient architecture protection significantly affect their original appearance and aesthetic value and finding wood elements that are similar to the ones in existing historic timber structures is not easy. Here we report a simple and effective method to archaize wood, Castanopsis sclerophylla, by ferric chloride (FeCl3) treatment without significantly affecting its mechanical properties and durability. The lightness and the color indexes of treated wood are similar to the ancient wood sample. The mechanical properties of FeCl3 treated wood are not statistically different from the control. Our durability testing results indicated that FeCl3 treated wood has good decay resistance against Irpex lacteus and Trametes versicolor with a mass loss of less than 10 %. This study provides a convenient method for the restoration and protection of ancient buildings.

Our goal was to determine physical properties and anatomical features in 33-year-old Hevea brasiliensis clones. We cut wood samples from clones LCB510, RRIM600, IAN873, IAN717 and GT1 planted in Selvíria, Mato Grosso do Sul, Brazil. We used standard techniques in wood studies. We found that clones differ in basic density, volumetric shrinkage and anatomical features, with the exception of ray width. Basic density, volumetric shrinkage, fiber length, fiber wall thickness, vessel element length and vessel diameter tended to increase from pith to bark, while vessel frequency propended to decrease. We conclude that wood of the studied clones has potential for industrial use.

The main objective of this study is to determine optimum cutting parameters in order to specify the effect of densification by compressing on the processing properties of solid wood material and to achieve the best surface quality in materials densified at different rates. In line with this goal, the widely grown and low-density black poplar (Populus nigra) tree species were selected as the experimental material. Samples, which were compressed and densified by Thermo-Mechanical method at 0 %, 20 % and 40 % ratios, were processed at 1000 mm/min, 1500 mm/min and 2000 mm/min feed speeds and in 12000 rpm, 15000 rpm, 18000 rpm rotation speed on a computer numerical control machine by using two different cutters. Surface roughness values (Ra and Rz) were measured in order to evaluate surfaces obtained. Smoother surfaces were obtained in computer numerical control machining of densified samples. The lowest surface roughness values occurred in 40 % densified samples, which were the densest. The lowest surface roughness was obtained when 40 % densified samples were processed with cutter no.1, at 1000 mm/min feed speed and at 18000 rpm.

In the production of particleboard, the chips emerging from the drying oven usually pass into the bonding process without sufficiently cooling down. Moreover, along with the effect of friction during the bonding process, the increased chip temperature boosts the consumption of resin/adhesive and affects the properties of the board. This study investigated the effect of chip temperature during the bonding process on the properties of particleboard. With this aim, the effects were determined for six different temperatures (25 °C, 30 °C, 35 °C, 40 °C, 50 °C, 55 °C) measured during the bonding of the chips. According to the results, optimum board properties were obtained from the groups in which the chip temperature measured during the bonding process was 30 °C – 40 °C. Furthermore, it was determined that chip temperatures of above 40 °C during the bonding process significantly reduced the mechanical properties.

This study evaluated the natural durability of seven imported hardwoods (bangkirai, burckella, ipe, jarrah, kempas, malas, and merbau) used for deck boards against decay fungi (Fomitopsis palustris, Gloeophyllum trabeum, Trametes versicolor, and Irpex lacteus) and the subterranean termite (Reticulitermes speratus kyushuensis) in accelerated laboratory tests. Ipe, jarrah, and merbau were very durable to fungal attack, with performance comparable to ACQ-treated wood. Bangkirai, burckella, kempas, and malas were classified as durable or moderately durable, depending on the fungal species tested. All wood species except for merbau were highly resistant to termite attack. Termite resistance was similar to ACQ-treated wood. Merbau showed somewhat less than all other species but still significant termite resistance. These results indicated that selected naturally durable hardwood species could inhibit fungal and termite attacks as effectively as ACQ treatment. The natural durability of wood species tested in this study is most likely due to the biocidal extractive content of the wood.

Eucalyptus planted forests contribute to maximizing lumber production but problems such as longitudinal growth strain can negatively influence the quality of the products. Knowing dendrometric variables and wood properties can help in the prediction of longitudinal growth strain, mainly with the help of artificial intelligence. Thus, the aim of this research was to evaluate the use of artificial neural networks to predict longitudinal growth strain in Eucalyptus trees based on dendrometric variables, spacing between trees and wood density. The longitudinal growth strain was measured in trees of four Eucalyptus clones planted in three spacings. The diameter and height of each tree were measured. The basic wood density was determined. Artificial neural networks were used to estimate longitudinal growth strain as a function of dendrometric variables, tree spacing and wood density. The results showed that the artificial neural networks presented good results for training and validation, with most of them resulting in high correlation coefficient values. The trained artificial neural networks showed a correlation coefficient above 0,56. Artificial neural networks showed that the variables clone and basic wood density were the ones that most contributed to the prediction of longitudinal growth strain. On the other hand, the spacing between trees, the height of the tree and the diameter at breast height were not relevant to predict growth stresses.

This work aimed to evaluate the physical-mechanical properties of Pinus oocarpa wood agglomerated panels produced with different levels (0 %, 25 %, 50 %, 75 % and 100 %) of wood replacement with bean residues. For this purpose, Pinus oocarpa wood and the agricultural residue were reduced into particles and their properties of apparent density, extractives, lignin and ash content of these raw materials were determined. Then, the particles were dried to a 3 % humidity and granulometrically selected to produce panels with a density of 0,60 g/cm3. These particles were bonded using 12 % urea-formaldehyde adhesive, pressed, following normative dimensions (250 mm x 250 mm x 15 mm (width, length, and thickness)), and kept in a climate-controlled environment (20 ºC ± 2 ºC and 65 % ± 5 % RH) until the physical and mechanical tests were carried out. The research results indicated that the particles from bean residues in comparison with Pinus oocarpa wood, presented low density, lignin and holocellulose values, and higher extractives data. Furthermore, regarding the characterization of the panels, there was a trend towards uniformity in the apparent density values, an increase in the properties of compact ratio, water absorption and thickness swelling, and a decrease in their mechanical properties associated with the increase in the by-product addition to the panels. Therefore, new studies are necessary, seeking a larger study and greater knowledge of the addition effects of bean residues in particulate panels, aiming the dissemination of this sustainable process on large scale.