Effect Of Wood Moisture Content Research Articles

Effect of wood moisture content and adhesive open time on the adhesion strength of wet bonded Pinus radiata wood

AbstractGluing wood in the wet state can reduce warping, splitting, and increase processing volume recovery. Adhesive open time and moisture content may play an important role in bond line strength, but there are no specifications for wet wood bonding. Wood specimens at two different moisture contents were glued with three polyurethane adhesives and tested in shear on the bond line. Open time of 15 min was superior to 4 and 40 min. All adhesives performed better when wood was glued at 30% moisture content than at 101%, but only the 15- and 40-min open time met the minimum shear requirement.

Effect of wood moisture content on the performance of wood burning cook stoves

ABSTRACT Rural Ethiopian communities rely mostly on biomass fuels for subsistence and productive purposes. With an increasing population and dwindling forest resources, wood fuel consumption has exceeded its supply. Besides, people do not know ways of maximising biomass efficiency. The study involves the burning efficiencies of woods with varied moisture contents. Eucalyptus wood of five different moisture contents was used in five identical wood-burning stoves purposefully constructed for this purpose. Tests were conducted over 5 days, thereby giving five replications. In the tests, food temperature, stove body temperature, and stove smoke outlet temperature measurements were conducted along with ambient air temperatures. Wood with 10% moisture content performs better during combustion with respect to low and high moisture content wood. High moisture content delayed the cooking onset and low moisture decreased the duration of effective cooking. The 50% moisture content or greater with respect to oven-dried wood failed to cook. Moisture content of around 30% delayed the time to reach cooking temperature by two and hence elongated the cooking time. There is also the extended smoke time as observed from the smoke outlet temperature.

Towards effectively restoring agricultural landscapes in East African drylands: Linking plant functional traits with soil hydrology

Abstract Land degradation is a major threat to food security in Sub Saharan Africa. Low infiltration rates in degraded soils increase the risk of surface runoff and decrease soil and groundwater recharge, resulting in further loss of soil fertility, water scarcity and crop failure. Increasing woody vegetation typically enhances soil infiltrability but little is known about how species may have differential effects on the soil hydrological properties. The aim of this study is to understand how woody vegetation and its functional properties affect soil fertility and infiltrability. We measured field‐saturated soil hydraulic conductivity (Kfs) and soil organic carbon (SOC) in 38 plots across agricultural landscapes in Muminji, Kenya. Woody vegetation and land use inventories took place and species functional traits were measured on the 63 most abundant species. We systematically tested the effects of vegetation quantity (aboveground woody biomass and vegetation cover) and quality (functional properties and diversity) on soil health (Kfs as a proxy for soil infiltrability and SOC for soil fertility). We found that both vegetation quantity and quality affected soil health. Aboveground woody biomass increased the Kfs and we found a nearly significant positive effect of vegetation cover on SOC. Woody plants with a low leaf thickness positively affected Kfs and a nearly significant negative effect of wood moisture content on SOC was found. Synthesis and applications. This study demonstrates that the systematic assessment of vegetation can lead to evidence‐based recommendations to guide land restoration. We found that avoiding bare soil and promoting woody plants, while favouring species with thin leaves and avoiding species with a very low wood density and water storage strategy, is beneficial for soil health across agricultural landscapes in East African drylands.

Testing of the fatigue strength along wood fibres at different moisture contents

Testing of the fatigue strength along wood fibres at different moisture contents. The paper determines the effect of wood moisture content on the fatigue strength in compression along fibres. The method of determining the maximum stress at the proportional limit was used for the measurements. Fatigue strength was investigated for three wood species: pedunculate oak (Quercus robur L.), bearded birch (Betula pendula Roth.) and Norway spruce (Picea abies L.), with two moisture contents: close to the absolutely dry state and above the fibre saturation point. The ratio of fatigue strength to short term strength depends on moisture content and is similar for birch (70.3% in the dry state and 72.1% in the wet state), for oak (67.4% and 69.5% in both states) and for spruce (66.6% in the dry state and 68.1% in the wet state). The moisture content of the wood clearly influences the fatigue strength of the wood. On average, the fatigue strength of wood with moisture contents above the fibre saturation point constitutes about 0.20 of the fatigue strength of wood with moisture contents close to 0%. This tendency was found regardless of the tested species. The simplified method for testing fatigue strength at the limit of proportionality has shown its limited usefulness, requiring further analysis and comparison with other methods in order to be thoroughly tested and possibly improved.

Influence of moisture content on the contact angle and surface tension measured on birch wood surfaces

Surface tension of solid wood surfaces affects the wettability and thus the adhesion of various adhesives and wood coatings. By measuring the contact angle of the wood, the surface tension can be calculated based on the Young-Dupré equation. Several publications have reported on contact angle measured with different test liquids, under different conditions. Results can only be compared if the test conditions are similar. While the roles of the drop volume, image shooting time etc., are widely recognized, the role of the wood surface moisture content (MC) is not evaluated in detail. In this study, the effect of wood moisture content on contact angle values, measured with distilled water and diiodomethane, on sanded birch (Betula pendula) surfaces was investigated, in order to find the relationship between them. With increasing MC from approximately 6% to 30%, increasing contact angle (decreasing surface tension) values were measured according to a logarithmic function. The function makes possible the calculation of contact angles that correspond to different MCs.

Effects of Wood Moisture Content and the Level of Acetylation on Brown Rot Decay

Acetylation is one of the most common types of wood modification and is commercially available throughout the world. Many studies have shown that acetylated wood is decay resistant at high levels of acetylation. Despite its widespread use, the mechanism by which acetylation prevents decay is still not fully understood. It is well known that at a given water activity, acetylation reduces the equilibrium moisture content of the wood cell wall. Furthermore, linear relationships have been found between the acetylation weight percent gain (WPG), wood moisture content, and the amount of mass loss in decay tests. This paper examines the relationships between wood moisture content and fungal growth in wood, with various levels of acetylation, by modifying the soil moisture content of standard soil block tests. The goal of the research is to determine if the reduction in fungal decay of acetylated wood is solely due to the reduction in moisture content or if there are additional antifungal effects of this chemical treatment. While a linear trend was observed between moisture content and mass loss caused by decay, it was not possible to separate out the effect of acetylation from fungal moisture generation. The data show significant deviations from previously proposed models for fungal moisture generation and suggest that these models cannot account for active moisture transport by the fungus. The study helps to advance our understanding of the role of moisture in the brown rot decay of modified wood.

Combined effect of wood moisture content, drill bit rotational speed and feed rate on drilling resistance measurements in Norway spruce (Picea abies (L.) Karst.)

ABSTRACT An IML-RESI PD 400 drilling tool and a standard spade drill bit (IML System GmbH, Wiesloch, Germany) were used to study the combined effect of wood moisture content (MC), drill bit rotational speed and feed rate on drilling resistance (DR) and feeding force (FF). Tests were made with Norway spruce (Picea abies (L.) Karst.) conditioned in a normal climate (20°C/65% RH), at 20°C/95% RH, vacuum-pressure impregnated in water, and oven-dried. Rotational speeds and feed rates had an impact on feed rate per cutting edge for the major cutting edge of the drill bit which was used for correlation with DR and FF for various MC. Impact of MC on DR and FF depended on rotational speeds and feed rates of the drill bit. For feed rates per cutting edge less than 0.09 mm, DR was higher for water saturated (WS) specimens. Negligible differences between DR for various MC were found for feed rates per cutting edge between 0.09 and 0.15 mm. DR was higher at low MC for feed rates per cutting edge which were higher than 0.15 mm. FF extremely increased in conditioned (20°C/95% RH) and WS specimens at feed rates per cutting edge less than 0.1 mm.

Effect of open assembly time and equilibrium moisture content on the penetration of polyurethane adhesive into thermally modified wood

ABSTRACTThe effect of wood moisture content and open assembly time on penetration of polyurethane (PU) adhesive into thermally treated Scots pine (195 and 210°C) was investigated according to effective penetration (EP) and maximum penetration (MP) measurements using fluorescence microscopy. For samples treated at 195°C, a higher EP was noted at 8.6% equilibrium moisture content (EMC) after both assembly times (15 and 30 min) while for samples treated at 210°C, increasing wood moisture content resulted in a significant decrease in EP at 12.5% EMC after 15 min assembly time. Extending open assembly time was found to increase the EP of PU adhesive only in the case of samples treated at 195°C and with 8.6% EMC. For samples treated at both treatment temperatures and after shorter open assembly time, the highest MP was observed at moderate EMC levels of 8.6 and 8.2% and the lowest at the higher EMC levels of 13.2 and 12.5%.

Effect of Wood Moisture Content in Edge Glued Panel Bonding for Furniture Industry: Analysis of Shear-Stress and Rupture in Bondline

The objective of this article was to study the influence of the Pinus taeda wood moisture content to the production of EGP (Edge Glued Panel) in the bonding stage, using PVA adhesive. It was analyzed the joint resistances through shear-stress tests and rupture in the bondline. The wood moisture classes adopted to the panels were: “A” ( [8%, 9%[ ), “B” ( [9%, 10%[ ), “C” ( [10%, 11%[ ), “D” ( [11%, 12%[ ) e “E” ( [12%, 13%[ ). After the panel production, it was sawn the specimens for the resistance shear in the bondline tests by traction. The tests results show that it was statistically significant differences to the values of rupture tensions between A class and B, C, D and E classes. The wood medium rupture presented a tendency to reduce with the moisture increase, and the total rupture in the bondline presented a small tendency of a less number of occurrences with the rupture tension increases.

The Effect of Moisture Content and Drying Temperature on the Colour of Two Poplars and Robinia Wood

The colour change of wood has been the topic of numerous research activities worldwide. This study investigates the colour change of Robinia (Robinia pseudoacacia L.) and two hybrid poplars, namely Pannónia poplar (Populus x euramericana cv. Pannónia) and I-214 poplar (Populus x euramericana cv. I-214). The sapwood and heartwood were investigated separately for each of the poplars. The heartwood of Robinia was also investigated. The timbers were dried in a climate chamber at four different temperatures (20 °C, 40 °C, 60 °C, and 80 °C), as the relative humidity was reduced in 5 steps (95%, 80%, 65%, 40%, and 20%) at each temperature. The colour co-ordinates L*, a*, and b* were measured according to the CIELab system. Differences in terms of colour change between wood species and sapwood versus heartwood are discussed in the paper. The effect of wood moisture content and heat on the colour co-ordinates is provided. The colour of Robinia is more sensitive to heat than poplar.

Factors Affecting the Temperature Increasing Rate in Wood during Radio-Frequency Heating

Radio-frequency (RF) heating has been widely used in the wood industriesand it is essential to understand the factors affecting the heating rates. In this article, Chinese fir (Cunning hamialanceolata) was heated with RF energy intermittently at 2 min per cycle to study the effect of wood moisture content (MC), sample thickness, and RF power level on heating rates. The study revealed that wood MC significantly affected the RF heating rate (p < 0.01). The heating rate was the highest (5.0°C/cycle) at an MC around the wood fiber saturation point (FSP). The heating rates were lower with a lower MC of 15% (0.89°C/cycle) and a higher MC of 70% (1.2°C/cycle). Lumber thickness did not have a significant effect on the RF heating rate at the center of the lumber; however, the heating rates at various locations along the thickness direction were significantly different. The temperature at the lumber center was 20°C higher than the temperature at 10 mm below the surface during heating. The heating rate for lower RF power level was initially greater than the rate at higher power RF level and then rapidly decreased. However, the heating rate at the higher RF power level remained constant during the whole heating process. RF power levels had a significant effect on the internal heating rate of wood (p < 0.01).

The effect of pre-softened wood chips on wood fibre aspect ratio and mechanical properties of wood–polymer composites

The objective of this work was to study the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio after compounding in a twin-screw extruder and on the mechanical properties of wood–polymer composites (WPCs). Composites with 50 wt.% wood content were manufactured using pre-treated and untreated wood chips. The effect of wood moisture content on composite properties was studied by using dried and undried wood chips. The mechanical properties and fracture surfaces of the composites as well as the microstructure and aspect ratio of wood particles after compounding were studied. The highest wood particle aspect ratio after extrusion was achieved by using pre-treated, undried wood chips as raw material. The chemical pre-treatment was found to enhance the defibration of wood chips as well as the mechanical properties of the composites.

Processing of wood chip–plastic composites: effect on wood particle size, microstructure and mechanical properties

Wood chips were used as raw material in extrusion of wood–plastic composites. Wood–plastic composites with ∼50 wt‐% wood content were manufactured by using two different compounding methods. Dried and undried wood chips were used to investigate the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step. Wood particle properties were measured using optical fibre analysis. Microscopical methods were used to examine the microstructure of wood particles. Furthermore, the prepared composites’ mechanical properties were studied. The particle size of wood chips was significantly reduced during extrusion in both processing methods. The undried wood chips had higher aspect ratios in comparison with the dried wood chips after extrusion. Despite the higher aspect ratio, the mechanical properties of composites manufactured with undried wood chips were not better than the properties of composites with dried wood chips.

A Note on the Effect of Wood Moisture Content and Clear Coating on the Color of Veneer Panels Stained with Solvent-Borne Stain

Red alder, mahogany, maple, white oak, and pine veneer panels conditioned to 6, 12, or 20 percent moisture content (MC) were stained with red solvent-borne stain, partially coated with clear lacquer, and air dried. All of the hardwood panels stained at an MC of 20 percent were either significantly redder or darker than panels stained at lower MCs. Clear coating made panels darker and redder (except oak). We conclude that large departures from the recommended MC for staining (6% to 8%) can significantly alter the color of hardwood veneer panels stained with solvent-borne stain.

Laboratory study of the effects of moisture content on heat transfer and combustion efficiency of three biomass cook stoves

The effect of wood moisture content on the performance and emissions of biomass-fired stoves was assessed using the laboratory-based water boiling test. This test yielded a number of performance indicators (time to boil water, specific fuel consumption and energy efficiency) when the stove was operated at both high and low power. When combined with emission measurements, combustion efficiency was investigated as well. This paper presents an integrated efficiency evaluation of the traditional open fire, an Aprovecho rocket stove from China and a “skirt” stove which were all tested each at 5%, 15% and 30% moisture content (wet basis) of wood. Results showed that an increase in moisture content increased efficiency up to a point. Extremely dry or over-wet fuel inhibited combustion efficiency. Overall, the type of stove exhibited a stronger effect on the total emissions than did the moisture level in the fuel.

Theoretical exploration of factors affecting dielectric constants of masson pine

AbstractA theoretical model to calculate the dielectric constant of masson pine (Pinus massoniana) in the longitudinal direction was developed by considering the effect of wood moisture content, density, ratio of earlywood to latewood, and the volume fraction of ray cells. The calculated results were used to explore the relationship between dielectric constant and moisture content, density, and other factors. The results indicated that the dielectric constant of masson pine increased with the moisture content. From 0% to 30% moisture content, the longitudinal dielectric constant increased more than 5 times from 2.3 to 13.3. In the range of density from 0.450 to 0.650 (g cm−3at 15% moisture content, the longitudinal dielectric constant increased from 7.7 to 10.0. However, the longitudinal dielectric constant decreased as the volume fraction of ray cells increased.

Study on the effect of wood moisture content on permeability in the hygroscopic range

In this paper, the relationship was studied bwtween the permeability of Pinus koraiensis, Larix gmelinii, Betula platphylla and Populus davidiana and moisture content of wood in the hygroscopic range. The mathenatical model of variation low has been obtained from the relationship between wood and water, The results are as fellow: (1)The relationship betweed wood permeability and the moisture content is in twice curve function in the hygroscopic rang. (2)There is a peak value in tangential permeability, (3) The number of openings per cm of cross sectionand pit—opening average radii reduces by the increaasing of wood moisture content.

The effect of wood moisture on infection of Sitka spruce stumps by basidiospores of Heterobasidion annosum

AbstractIn an inoculation experiment to test the effect of wood moisture content on infection of Sitka spruce (Picea sitchensis) stumps by basidiospores of Heterobasidion annosum, exposure to high rainfall increased infection in the heartwood and reduced sapwood infection compared to covered stumps. This was associated with a greater moisture content in both wood types. Within‐treatment variation in the amount of infection was high and it is suggested that endogenous factors in stumps may have a greater influence on infection than the environment or the availability of spores.

Reliability of Bolted Wood Connections

This report analyzes the implied reliability of current practice for the design of bolted wood connections. All U.S. data available to the writer were used. The resistance distribution was taken to be normal, and the coefficient of variation was obtained by pooling data from several sources, as long as the moisture condition, grain direction, side‐plate material, and species were alike. The reliability index for softwood connections is about 5; the index for hardwood connections is about 20% greater than that for softwood connections. A comparative study of data from six sources showed that reliability does not depend upon bolt length‐to‐diameter ratio, and the effects of wood moisture content and side‐plate material (steel or wood) are minimal. Two new codes are briefly examined and compared with current practice. Both of these codes contain radically reformed design criteria for bolted wood connections. The comparison shows that both new codes maintain the present level of reliability.

The Effect of Wood Moisture Content on the Emergence of Southern Lyctus Beetle12

The Effect of Wood Moisture Content on the Emergence of Southern Lyctus Beetle12