Papers by Keyword: Wood

Abstract: Brazil has an infinity of native species that provide wood with good properties for use in civil engineering, industries and other segments. Schizolobium amazonicum Wood is a species that is much used in Brazil to manufacture of wood based-products. Researches regarding the properties are being performed in order to rationalize their use. The aim of this research is to determine the hardness of the Schizolobium amazonicum Wood in directions parallel and normal to the grains. The tests occurred in accordance with the Brazilian Code ABNT NBR 7190: 1997. The average values determined were interesting hardness upon the low specific gravity presented by Schizolobium amazonicum Wood.

Abstract: To prohibit wood hygroscopicity, changing naturally hydrophilic wood surface into hydrophobic surface is essential. To achieve this goal, one possible approach is to coat nanostructured metal oxides on wood surface. In this study, wood surface coated by ZnO nanorod arrsys (ZNAs) was successfully fabricated using a hydrothermal method with subsequent modification by a thin layer of n-dodecyltrimethoxysilane (DTMS). SEM images showed uniformly large-scale ZNAs were grown onto the wood surface. XRD patterns confirmed that the ZNAs were the hexagonal wurtzite phase. The wettability of the ZNAs modified wood sample was evaluated by water contact angle (WCA) measurements. The ZNAs modified wood was found to exhibit superhydrophobicity with a WCA of about 156° and a sliding angle of around 2°, which could resulted from the proper surface roughness and lower surface energy. These results demonstrated that hydrothermal method was a feasible method to create superhydrophobic wood.

Abstract: According to the traditional theory of elasticity, the total deflection of a beam occurs due to the combined effect of both the bending moment and the shear force. In isotropic materials such as steel and concrete, the deflection due to shear is usually not taken into account since it represents only 1% of the total deformation approximately. However, in anisotropic materials such as bamboo, the deflection due to shear should be taken into account because it may represent more than 20% of the total deformation of the beam. To better predict the influence of the shear effect on the deflection of bamboo beams, the longitudinal Young ́s modulus and the shear modulus of Guadua angustifolia were determined through the application of repeated three-point bending tests of whole culms and small prismatic elements while aligning their length along the axial direction of the culm. In order to determine the value of the shear modulus, each test was carried out using four different spans. The end results for the culms were: the longitudinal modulus of elasticity E equal to 23525 MPa, and the shear modulus G equal to 298 MPa. Thus, the substantial difference between the Young ́s modulus and the shear modulus confirms the high anisotropy of bamboo, and results indicate that shear deformation should always be included for the calculation of deflections of bamboo structures. Furthermore, the significant differences between these values and those obtained with the small prismatic elements may be attributed to the anisotropy and heterogeneity of the material. However, more tests have to be accomplished to further corroborate these results and find other anisotropic elastic properties of the material.

Abstract: Natural fibres have recently raised attention for presenting adequate mechanical characteristics for the reinforcement of wood structural elements. The use of both natural fibres, in laminated beams and wood from reforestation, is in accordance with the current economic interest and sustainable appeal. This paper focuses on the analysis the viability of sisal fibre use, in wood laminated structures as a reinforcing material, taking three methods into consideration: Stress functions, Classical lamination theory and Transformed section method. The laminated beams were reinforced by sisal strips with a thickness of 2 mm and constituted by the species of wood: Pinus (Pinus sp). Each lamina has the following dimensions: width of 5 cm, height of 10 cm and length of 150 cm. It was noted that the differences between the results from the classical lamination theory and transformed section method were, in an average of 14 % and 16 % for normal and shear stresses respectively. The difference of 12 % for displacements is a normal result taking into account that the span used is considered high for this wood species. In relation to the stress function method, the differences are minimal, around less than 1% for all analyses. It was also noted that the beam with reinforcement presented a decrease of the values of normal and shear stresses and displacements in relation a beam without reinforcing fibres. This decrease was of the order of 8% for the normal and 5% for the shear stresses and 12 % for the displacements In general, the strengthening of wood laminated beams with sisal fibres is more effective for structures that are used only in wood structural elements, in which the elastic modulus is at least equal to these fibres.

Abstract: Wood is one of the completely renewable natural materials. Thanks to its unique properties, many experts consider wood to be a building material of the 21^st century. Characteristics of its qualities. The most commonly used wood based structural systems. Examples of realized wooden buildings.

Abstract: Wood belongs among one of the oldest building materials in Slovakia. Historically, it has been used mainly in traditional folk architecture, however in many forms; as a structural and expressive material, it is an inherent part of representative historical architecture. Considerable decline in the use of wood as structural material started in the 2^nd half of the 20^th century, when building construction industry turned to more progressive materials such as concrete, steel, aluminium, plastics and glass.

Abstract: Increased use of alternative fuels in cement kilns is a trend in the world. However, replacing fossil fuels like coal with different alternative fuels will give various impacts on the overall kiln process due to the fuel characteristics. Hence, it is important to know to what extent the fossil fuels can be replaced by different alternative fuels without severely changing process conditions, product quality or emissions. In the present study, a mass and energy balance for the combustion of different alternative fuels in a cement rotary kiln was developed. First, the impact of different fuel characteristics on kiln gas temperature, kiln gas flow rate and air requirement were observed by using coal (reference case), meat and bone meal (MBM), two different wood types, refuse derived fuel and a mixture of saw dust and solid hazardous waste as the primary fuel. It was found that the key process parameters depend largely on the chemical characteristics of the fuel. It appears that MBM shows quite different results from other alternative fuels investigated. Next, simulation of combustion of a mixture of coal and MBM in the main burner was carried out in three steps. The first step was combustion of replacing part of coal energy with MBM, and a reduction in kiln exhaust gas temperature compared to the coal reference case was found. In the second step, the fuel feed rate was increased in order to raise the kiln gas temperature to that of the reference case. In the third step, the fuel feed rate and the clinker production rate were changed in order to have not only the same kiln gas temperature but also to obtain the same volumetric flow rate of total exhaust gas from the precalciner as in the reference case. Around 7% of reduction in clinker production rate could be observed when replacing 48% of the coal energy input. Results from a full-scale test using the same mixture of coal and MBM verified the simulation results.

Abstract: To know the physical and mechanical properties of wood to be employed as structural elements in is an important factor for its use in a rational way. The connections between members of timber structures are also relevant topic once local stress concentrations can occur and safety must be seriously taken in account. Brazilian Code ABNT NBR 7190: 1997 "Design of Timber Structures" provides guidelines for connections calculation based on two alternative limit states: wood strength to embedment or bending of the bolt. The purpose of this paper is estimate the strength to embedment of Pinus sp. to bolts in three directions with respect to the grain: parallel, perpendicular and inclined at 45o. Specimens obeying requirements of Brazilian Code related to bolts diameter (10mm) were prepared and tested. The embedment strength in parallel direction to the fiber was the highest and the failure modes were more frequent crushing and cleavage.

Abstract: To investigate the effect of the additive agents such as polyethylene glycols (PEGs), melamine formaldehyde resin (MF-resin) and phenol formaldehyde resin (PF-resin) on the flow deformability of solid wood, free compression tests during heating were performed. Various molecular weights ranging from 200 to 20,000 for PEGs and almost similar molecular weight around 380 for MF-resin and PF-resin were applied. It was found from the compression tests that the yield stress indicating wood cell deformation resistance was drastically decreased with smaller molecular PEGs in wood, whereas the initiation of flow behavior, which is derived from detachment/slippage between cells, occurred at lower pressure with larger molecular PEGs. For generating the flow behaviors of solid wood, smaller molecular resin/substance was not always suitable. Thermosetting agents also act as a plasticizer during heating and especially the PF-resin showed better softening effect as well as a promoter of flow behavior than the MF-resin with almost similar molecular weight. This indicates that it is important for generating flow behavior to consider affinity/compatibility of resin to wood constituents. A maximum flow deformation ratio in the tangential direction of wood reached 180 % when using PEG 20,000 and MF-resin as an additive agent. It was also demonstrated that using PF-resin and MF-resin deep cup products shaped by a backward extrusion process had a better size stability against water, steam, and acetone.

Abstract: Wood as a basic building material was used in the past. It was used for construction of roofs, windows, doors, ceilings as well as for building of whole houses and outbuildings, mostly in the countryside and mountains. Wood is an organic product, which does not last forever. In case of appropriate condition it could be degraded by atmospheric impacts, plants and animal organisms.