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

Weight-strength optimization of wooden household chairs was performed based on the member section size in this study. Member section sizes of the Scotch pine (Pinus sylvestris) and Oriental beech (Fagus orientalis) chairs were optimized and resulting re-manufactured optimized chairs were tested under the cyclic “front to back”, “back to front” and “backrest” loads according to American Library Association (ALA) specification. Finite element method (FEM) and MATLAB nonlinear programming were utilized for the optimization. Firstly, the internal forces and moments acting on each member were analyzed by FEM in order to obtain the maximum critical stresses in each type of member; then, optimized cross-sectional sizes of the members were determined by Gradient Descent method, and all constraints were treated with Logarithmic Barrier Functioning. As a result, the minimum section sizes of members were determined, and cyclic performance tests were performed to determine whether the optimized chairs were strong enough to carry the acceptable loads. According to the results, member section size of both beech and pine chairs could be significantly reduced. The reduction was 32 % in the total weight and volume for beech chairs while 16 % for pine chairs without sacrificing the performance required for domestic usage by ALA. In conclusion, the method used is suitable for the optimization of furniture frames, making it lighter and reducing the material costs. 

Red pine (Pinus brutia) wood particles and dolomite mineral were used in varying proportions to form mineral-added gypsum particleboards. Mechanical, physical, and chemical properties of the boards were tested. The increasing  mineral content was found to improve the water absorption properties but the increased amount of  gypsum  in the mixture negatively affected the thickness swelling and water absorption properties. The usage of dolomite mineral in the board composition increased the internal bond properties and higher than the standard of 0,28 MPa. However, all types of boards had modulus of elastic, modulus of rupture and thermal conductivity results values below the standards.  Moreover, the thermal conductivity values decreased in all board types because of the reduction of the mineral dolomite. Thermal gravimetric analysis, Fourier transform infrared spectrometry tests were applied to examine the thermal and flame retardancy properties of inorganic materials, wood-gypsum composites, which are used at different rates for synergistic effect. The gypsum and dolomite amount affected the thermal variation, whereas the increment in the weight of the wood particles also increased the thermal degradation. It was determined that stresses at 850-980 cm-1 reveal Ca-O and Mg-O, reveal at 881cm-1 C-OH, weak vibration at 1619 cm-1 and a strong bond structure in the 1445-950-882 cm-1 bands. These bands express the characteristic presence of the CaO and MgO belonging to dolomite. The study demonstrated the feasibility of producing mineral-based gypsum board products using wood chips.

A renewable tannin-based resin adhesive with enhanced bonding strength, good water resistance and long storage life has been prepared based on tannin, furfural and furfuryl alcohol coming from forest and agricultural products. Fourier transform infrared spectroscopy (FT-IR), Electrospray ionization mass spectroscopy (ESI-MS) and Differential scanning calorimetry (DSC) indicated that furfuryl alcohol and furfural can react with tannin under acidic conditions, with the involvement of –CH2–O– groups in the cross-linking of tannin-furfuryl alcohol-furfural resin (TFF) adhesive. The gel time of TFF was longer than that of tannin-furfural resin (TF), while the shear strength of TFF-bonded plywood suggested that the cured TFF adhesive acquired a performance superior to that of tannin (T) and TF adhesives. Furthermore, water resistance of TFF adhesive could be further enhanced with respect to T and TF adhesives through cross-linking with 3 % epoxy resin (EPR).

El objetivo de este trabajo fue evaluar la variación radial de la morfología de las traqueidas de pinos híbridos. Se extrajeron tarugos radiales de árboles de pino híbrido “F1 INTA-PINDO”, en dos ensayos. Las muestras se tomaron a 1,30 m de altura, se disociaron y se midieron las características anatómicas de las traqueidas individuales obtenidas de la fracción de madera tardía de los anillos de crecimiento 4, 7, 10 y 11 mediante microscopía óptica con análisis de imagen. Para la obtención del ángulo microfibrilar se utilizó la técnica "a través de las puntuaciones en traqueidas individuales”. Para el ángulo microfibrilar dentro de cada edad, se encontraron diferencias estadísticas significativas entre sitios y familias para un nivel de confianza del 95 %, mientras que las variaciones no fueron significativas para las demás propiedades estudiadas. Se observaron cambios importantes en la morfología celular de las traqueidas para las edades consideradas. Los valores medios de ángulo microfibrilar, ancho del lumen y ancho total de las traqueidas disminuyeron con la edad, independientemente del sitio y las familias evaluadas. Los valores medios de espesor y la proporción de pared celular aumentaron con la edad. Estos resultados indican que las propiedades de la madera no serían uniformes en el sentido radial y deben ser tenidas en cuenta al momento de utilizarlas para determinados usos. Se identificaron familias con mejor performance en crecimiento y parámetros deseables para la calidad estructural de la madera, las mismas pertenecen a las mejores posiciones del ranking genético de crecimiento. Se concluye que, a los 11 años de edad este taxón produce madera madura, debido a las características de su morfología celular.

Tree growth is influenced by various environmental factors that lead to anatomical, physical and chemical changes in their wood. Reaction wood is one of the tree's reactions that make many restrictions in wood usages. Reaction wood in broadleaf is called tension wood. This study was aimed to stimulate the formation of tension wood in two-year-old seedlings of Populus alba by using intermittent bending, nitrogen fertilization and gibberellin hormone. The application of different treatments increased the content of cellulose compared to the control sample. Meanwhile, the bent specimens had more increase while the straight specimens had no significant difference in the statistical grouping. The content of lignin decreased in all treatments compared to the control sample. The cellulose/lignin ratios obtained from ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) analysis of wood sawdust and chemical composition measurements were almost close to each other and were higher in the treated samples than in the control. The degree of crystallinity obtained from XRD (X-ray Diffraction) measurements showed that all samples under intermittent bending had a significantly higher degree of crystallinity than the control sample, while this increase was not significant in all straight samples compared to the control sample. In general, it can be concluded that intermittent bending treatment had a greater effect on the stimulation and changes of chemical properties of tension wood in poplar and the application of nitrogen fertilization and gibberellin hormone increased this effect. The formation of gelatinous layer in the innermost part of the intermittent bent seedlings fiber cell wall was visible in light microscope images.

The objective of this study was to develop predictive expressions for estimating the withdrawal force capacity of various size of beech (Fagus orientalis) dowels from medium density fiberboard (MDF) and particleboard (PB). Furthermore, effects of the base material type, dowel diameter, dowel penetration and adhesive type on withdrawal force capacity were investigated. Polyurethane (PU), polyvinyl acetate based D2, and polyvinyl acetate (PVA) adhesives were utilized for gluing of dowels. A total of 540 specimens were prepared for edge and face withdrawal force capacity tests including two material types (MDF, PB), three dowel diameters (6 mm, 8 mm, 10 mm), three dowel penetration depths (15 mm, 20 mm, 25 mm for edge, 6 mm, 9 mm, 12 mm for face), three adhesive types and five replications for each group.  Specimens were tested under static withdrawal forces. Based on results of tests, predictive expressions that allow furniture engineers to estimate edge and face dowel withdrawal force capacity as a function of dowel diameter and dowel penetration were developed. Calculations showed that the expressions developed provided reasonable estimates for withdrawal force capacity of dowels. As a result of statistical analyses, material type, dowel diameter, dowel penetration, adhesive type and their four-way interaction have significantly affected the withdrawal force capacity of dowels. Test results also indicated that PU adhesive and MDF ranked the highest withdrawal force capacity among the adhesive and material types. Increasing either dowel diameter or penetration tended to have a positive effect on withdrawal force capacity. Dowel diameter was found to have a higher effect on withdrawal force capacity than dowel penetration.

Wood fiber filled high density polyethylene composites (WPCs) were prepared using twin screw extruder and maleated polyethylene as a coupling agent. Bamboo fibers were initially treated with alkali (NaOH), boric acid - borax (Ba-Bx) and borax (Bx). The treated and untreated fibers were used in combination with ammonium polyphosphate (APP) to investigate their synergistic effects on thermal stability, flame retardancy and mechanical properties. Alkali pretreatment (5 % NaOH) of fibers showed significant improvement in performance of APP by increasing thermal stability in WPCs. The derivative thermogravimetric (DTG) results indicate significance of Ba-Bx in promoting char induction at lower temperatures (340 ºC) and thereby, improved the thermal stability in WPCs. Flammability decreased with addition of flame retardant additives. As compared to pure WPCs, composites containing APP 10 % / Ba-Bx 5 % exhibited maximum reduction in average heat release rate (HRR) by 69 %, peak heat release rate (PHRR) by 59 %, total heat released rate (THR) by 48 % and also increased time to ignition (TTI) by 62 %. However, no significant difference was found among the combinations i.e., APP with or without compounds towards reducing the flammability of WPCs. The strength properties also reduced significantly when boron compounds were added along with APP. In general, APP alone (15 %) is enough for imparting thermal stability and flame retardancy in WPCs.    

Due to the advantages of short treatment period, no wastewater and oil produced, the CO2 laser is applied as an environment friendly thermal treatment for wood materials to improve the wood properties, such as appearance, color and wettability, etc. However, the morphological features of treated wood surface are also changed, which have negative effects on wooden product properties. To reveal the change tendency of surface roughness during laser irradiation, the common indexes of average roughness (Ra) and mean peak-to-valley height (Rz) were chosen to evaluate the surface roughness. The response surface methodology was selected to arrange the experiments and analyze the influences of laser parameters on surface roughness. The results showed that the poplar wood got rougher with the increased laser power, but the surface roughness decreased with increased feed speed and path spacing, due to the total heat absorption varied under different combination of laser parameters. The ANOVA results showed that the selected quadratic models for Ra∥, Rz∥, Ra⊥ and Rz⊥were significant due to the values of probability value (“Prob>F”) less than 0,05. In this case, all the input laser parameters were also the significant model terms for variation of surface roughness. The values of correlation coefficient were very close to 1, which meant the selected quadratic models could give accurate prediction of surface roughness for laser treated wood. Therefore, it is of great significance to predict the surface roughness of the modified wood surface scientifically and to guide the selection of reasonable modification process parameters.

Mycelium composites consist of particulate lignocellulosic materials, e.g., sawdust from the timber industry structured as a solid matrix resulting from the mycelial growth. Many protocols have been proposed based on different strains and substrates. However, the influence of intrinsic elements, such as the structure of the hyphal system on the main parameters required by the industry still needs to be researched. The main goal of this work is to assess the performance of five Patagonian lignocellulolytic fungal species for producing mycelium composites. Strains of these species were studied in order to assess the relation between basidiome hyphal structure and the hyphal structure of mycelium-based materials. Comparisons of the hardness in the Janka scale were performed with commercial expanded polystyrene. Composites resulting from the growth of Pleurotus ostreatus, Nothophellinus andinopatagonicus and Funalia trogii successfully formed composites, showing alower quality than Ganoderma australe. Ryvardenia cretacea in turn completely failed to colonize the substrate. The material resulting from the growth of Ganoderma australe on pine sawdust (a substrate chosen based on its local availability) is proposed as a good substitute with improved resistance.

Wood vinegar is a natural organic pesticide that is effective against plant diseases and harmful insects and is used in agriculture in particular for the improvement of plant and soil quality. In different application areas, wood vinegar provides effective protection against various harmful bacteria, fungi, and insects. Based on its demonstrated protection as a pesticide and antifungal, this study aimed to use wood vinegar as an impregnation agent in wood materials. For this purpose, using the full-cell process, Scots pine (Pinus sylvestris) and Eastern beech (Fagus orientalis) samples were impregnated with concentrations of 1 %, 5 %, 3 % and 6 % oak wood vinegar, obtained via the pyrolysis of sessile oak (Quercus petraea L.) wood at 350 °C. The samples were then subjected to tests for brown-rot (Serpula lacrymans) and white-rot (Trametes versicolor) fungi according to EN 113 (1996) standard, for Hylotrupes bajulus (Coleoptera: Cerambycidae) larvae according to EN 47 standard, and for three different mold fungi (Aspergillus niger Tiegh JAG-04-1003, Penicillium brevicompactum Dierckx FS-31, and Trichoderma harzianum Rifai FS-19). According to the results, the wood vinegar was found to exhibit antifungal, antimold, and larvicidal properties and consequently, could be used effectively in wood protection.