Influence Of Wood Moisture Content Research Articles

The Impact of Wood Moisture Content on the Productivity and Costs of Forest Energy Supply Chains in Southeast Brazil

Using wood for power generation necessitates a more efficient production chain in the various steps: harvesting, forwarding, storage, chipping, transport, and conversion systems. In this context, the moisture content (MC) of wood can impact the harvesting operation, the volume to be chipped, the transportation of raw materials, the storage time, and other factors, thereby influencing the economic aspects of the chain. The primary objective of this study is to investigate the influence of wood moisture content on the yield and costs of different forest operation chains for power generation in São Paulo State, Brazil. Our findings reveal that harvesting and forest transport are the primary cost components (over 80%) in the supply chains under study. We observed a difference of up to 17.6% in the unit cost of the energy generated among the studied supply chains. In economic and sustainable terms, our results suggest that logs should be stored in the field for three to four months and the transport distance to the power plant should not exceed 100 km.

The Influence of Processing Conditions on the Quality of Bent Solid Wood from European Oak

Bending of solid wood from European oak is one of the most demanding technological processes due to its specific structural and physical properties and variability. We investigated the influence of wood moisture content (MC) and stiffness, determined by NDT, as well as previous drying methods on the bending ability of the wood. The best quality was obtained with bending specimens bent at a moisture content of at least 16% and quarter- or semi-quartersawn. The number of rejected specimens increased slightly when HF bending was used. Single-stage predrying of oak to a final MC of 8% resulted in a high rejection rate (>70%) regardless of drying technique. The acceptance rate was higher for less stiff specimens where the ratio of ultrasonic velocity in the straight (vS) and bent region (vB) was less than 0.5 (vB/vS).

Compression parallel to grain of pinewood specimens with simulated damage by holes: Experiment and modeling

This work aims to clarify ideas about the mechanical behavior of pinewood (Pinus Sylvestris) with artificial damage in the form of holes under uniaxial compression parallel to the grain. Research methods: experimental (SHIMADZU test machine) and modeling using nonlinear equation. Comparison of the compression behavior of 15 specimens along the grain shows that the pre-peak branches of the load-displacement curve for specimens with and without holes do not differ significantly. However, at the post-peak stage, the failure of specimens without holes is smoother compared to the failure of specimens with holes. This pattern is clearer for specimens with two holes compared to specimens with one hole. In the experiments, the fracture zone of all specimens with holes passed through the hole. This pattern indicates that damage and degradation starts near the holes and due to the decrease in cross-sectional area and the effect of stress concentration near the holes. The simulation results are in agreement with experiments and data known from the literature. Nevertheless, it is advisable to continue the study taking into account the influence of wood moisture content, species and other factors.

The Influence of Wood Moisture Content on the Processes of Freezing and Heating

In wood processing, wood is exposed to an environmental temperature of less than 0 °C for some time, which mainly occurs during the air drying of wood in the winter months, or when lumber is stored in wood piles outdoors before the kiln drying process. In these cases, the wood freezing process increases the degree of freezing of the wood, subsequently significantly affecting the process of its heating during further processing (for example, in the cutting process). The most common method is heating by humid air, during the hot air drying of wood. We analyzed the temperature profiles on a cross-section of wood and moisture losses due to the freezing process and the size of moisture gradients. We compared theoretical calculations of the time required for defrosting and heating of wood with the experimentally measured values. The results show that the moisture content (MC) of wood has a remarkable effect on the wood freezing process. In samples with an average MC of 35.47%, the temperature drop was faster. After 10 h, the temperatures on the entire cross-section of the samples reached the lowest value of −13.2 °C. In samples with an average initial MC of 81.38%, three stages of temperature reduction in the wood were observed. The temperature dropped and the lowest temperature of −20.11 °C was reached after 24 h. The defrosting and heating process of samples with lower MC was significantly easier. The desired temperature of 65 °C in the middle of the samples was reached in 2 h and 20 min. The total time to defrost and heat the second group of samples (MC > FSP) was 3 h 30 min.

Multi-scale characterization of moisture and thermal cycle effects on composite-to-timber strengthening

The paper examines the influence of moisture and temperature cycles on timber elements reinforced with a wet lay-up system composed of various fibrous materials (carbon, flax) and matrices (epoxy resin, vinyl glue). A multi-scale experimental approach was adopted, including: (i) mechanical characterization of the composite reinforcement systems; (ii) investigation of behavior at the composite-to-timber interface by mechanical bond tests and microstructural analyses; (iii) four-point bending tests on strengthened timber beams. The results highlighted the good performance of natural-fiber composites compared with synthetic ones, and the marked influence of wood moisture content and temperature on bonding.

Modeling of a Biomass Gasification CHP Plant: Influence of Various Parameters on Energetic and Exergetic Efficiencies

This paper presents a theoretical assessment of energy, exergy, and syngas cleaning performances in a biomass gasification combined heat and power (CHP) plant with varying operating parameters. The analysis is carried out using a detailed model of a biomass gasification CHP plant developed with Aspen Plus. The model describes: wood drying and gasification in a dual fluidized bed (DFB) reactor, syngas cleaning, as well as combustion in a gas engine for electricity production. Heat is recovered from the CHP system for internal needs and for district and domestic water heating. An accurate prediction of tar and inorganic contaminants is developed for proper modeling of syngas cleaning efficiency. The influence of wood moisture content, drying conditions, flow rate of the sand circulating in the DFB reactor, catalyst and scrubbing agent efficiencies, as well as additional electricity production through steam turbine on the overall process performances is studied. On the basis of the comparative analysis of ni...

X-Lam Panels in Swimming-Pool Building – Monitoring the Environment and the Performance

The cross-laminated timber panels (X-Lam panels) are produced for structural use in Service Classes 1 and 2 conditions, in accordance with what is established on Eurocode 5 [. Timber boards are glued together on orthogonal layers, allowing the panel to perform two important characteristics: good dimensional stability and loading in two-way directions. The influence of wood moisture content on the feasibility of cross-laminated timber is described in this paper regarding the dimensional stability of the panels when applied in high moisture locations. Several European Technical Approvals, state the low importance of the dimensional variations with moisture content of this type of panel, but some reference values can be found in other technical documents. The French Avis Technique [[[1 reference the value of 0.01mm/m for in-plane deformation (per percentage of timber moisture variation) and the TRADA Wood Information Sheet, WIS 2/3-62 [1, refers the maximum value of 0.02mm/m for the same conditions.The use of the X-Lam panels in Service Class 3 can not be used, concerning the high level of stressing in glue lines, and no producer has yet certified it for this Service Class. Moreover, the French Avis Technique doesnt allow the use of X-Lam panels in swimming-pools due to high hygrometry, even for conditions corresponding to Service Class 2.Cross laminated timber panels are widely used across Europe but are giving the first steps in Portugal at the moment. The first big project was finished in spring 2012 in Almada, comprising a building integrating a 25 meter in-door swimming-pool and a gym. In order to assess the behavior of the timber structure, due to the non-conventional using of the X-Lam panels, a monitoring program was started immediately after building construction. The results obtained are presented and discussed in this paper.

Moisture content of wood: influence on mechanical behaviour of wood filled impact limiters and importance for quality surveillance during manufacturing

The moisture content of wood is known to have a significant influence on the wood’s mechanical properties. Using wood as an energy absorber in impact limiters of packages for the transport of radioactive material, it is of particular importance to ensure the moisture content and thus relevant mechanical properties to be in specified limits. The paper surveys the influence of wood moisture content on the mechanical properties of wood. Different measuring methods are discussed with respect to in situ applicability, accuracy and effort. The results of an experimental analysis of the accuracy of hand held moisture metres using the electrical resistance method are discussed. Conclusions are drawn regarding the measurement of moisture content of wood upon delivery as well as of complete impact limiter assemblies. Requirements for quality surveillance during manufacturing of wood filled impact limiters are derived and it is exemplified how to meet them. Construction, manufacturing and inspection of impact limiter encapsulation with regard to leak tightness are addressed.

Influence of wood moisture content on the modulus of elasticity in compression parallel to the grain

Brazilian Standard ABNT NBR7190:1997 for timber structures design, adopts a first degree equation to describe the influence of wood moisture content. Periodically, when necessary, the referred standard is revised in order to analyze inconsistencies and to adopt considerations according new realities verified. So, the present paper aims to examine the adequacy of its equation which corrects to 12% of moisture the values of rigidity properties obtained on experimental tests. To quantify the moisture influence on modulus of elasticity, it was applied tests of compression parallel to the grain for six specimens of different strength classes, considering nominal moisture of 12; 20; 25; 30%. As results, modulus of elasticity in the moisture range 25-30% showed statistically equivalents, and was obtained a first degree equation to correlate the studied variables which leads to statically equivalent estimations when compared with results by ABNT NBR7190:1997 equation. However, it was indicated to maintain the current expression for the next text of the referred document review, without prejudice to statistical significance of the estimates.

Study on the Solid Edge Banding Cracking of Panel Furniture

With the development of wood processing technology, panel furniture is getting more and more popular, where solid wood is often used for the edge banding to keep the natural wood grain, feel and colour. However, part of the panel furniture, especially that made in the south but sold to the north, has banding cracking issues due to various reasons. In this paper, on the base of comprehensive reference analysis and in-field exploration, the potential factors leading to banding cracking is studied; the influence of wood moisture content and adhesive on the cracking is specially analyzed; and the suggestions on the drying of the solid wood, glueing, manufacturing environment and process are presented. Thus, a new systematic concept to solve edge banding cracking is established, the study on which will be helpful to the development of panel furniture.

Influence of wood moisture content on bending and shear stiffness of cross laminated timber panels

The bending and shear stiffness of cross-laminated timber (CLT) made from softwood depend on the moisture content of the panel. In principle, the stiffness properties drop with increasing moisture content within the hygroscopic range. However, swelling provokes closing of open gaps of the middle layers and leads to an apparent increase of stiffness due to internal friction. This increase in stiffness is only relevant for low deflections and can provoke misinterpretation of measuring results when deriving stiffness properties of CLT by means of dynamic methods such as modal analysis. Drying, on the other hand causes cracking within CLT, which manifests itself in a distinct reduction of the bending stiffness perpendicular to the grain direction of the face layers. Calculating bending stiffness of CLT perpendicular to the grain direction of the face layers by means of the compound theory not taking into account the face layers therefore is a common and correct procedure.

Influence of wood moisture content and wood temperature on fungal decay in the field: observations in different micro-climates

In this study, Scots pine sapwood (Pinus sylvestris L.) and Douglas fir heartwood (Pseudotsuga menziesii Franco) specimens were exposed in double layer field trials at four different exposure sites and under different exposure conditions (in total ten test sets). The material climate of wood in terms of wood moisture content (MC) and wood temperature was automatically monitored over a period of 6 years and compared with the progress of decay. The aim of this study was to highlight the interrelationship between microclimate, material climate, and decay as a basis for the establishment of dose-response functions to be used for service life prediction of wood and wood-based products. Differences in resulting decay dynamics between the test sites as well as between the different types of exposure were quantified and discussed with respect to corresponding microclimatic and material climatic conditions. The time between the beginning of exposure and the first occurrence of visible decay varied between the sites and influenced the total decay development. The fundamental importance of direct decay factors, such as MC and wood temperature, were underlined and basic requirements for establishing dose-response-functions to be used in service life prediction models were derived.

Application of dielectric analysis for monitoring the cure process of phenol formaldehyde adhesive

Dielectric analysis (DEA) was conducted for continuous in-process monitoring of the curing of phenol formaldehyde (PF) adhesive. The influence of wood moisture content (MC) on the dielectric signal obtained in the PF adhesive bond was examined. The cure kinetics of the PF adhesive was evaluated at five different press temperatures, ranging between 120 and 200 °C. The results showed that dielectric changes monitored by a LCR meter (impedance analyzer) and fringe-field sensor were related to the PF adhesives cure—which involves chemical reaction and water movement/diffusion from the adhesive bond line—but not related to the changes of the moisture in the wood. The rate of cure was strongly affected by the press temperature. The higher press temperatures induced a faster temperature rise in the PF adhesive bond, and thus accelerated the curing process. An nth-order kinetic equation was fit to the DEA degree of cure data to demonstrate the utility of DEA to characterize PF adhesive cure.

Influence of wood moisture content on the intensity of free radicals EPR signal

In this paper the influence of wood moisture content on the intensity of the free radicals electron paramagnetic resonance (EPR) signal in wood is described. Intensity of the free radicals EPR signal significantly correlates with wood moisture content.

Untersuchungen zum Einfluss der Holzfeuchtigkeit auf das Bruchverhalten von Fichte bei Zugbelastung in Faserrichtung | The influence of moisture content on the fracture behaviour of Norway spruce when tension is applied in the direction of the grain

The influence of wood moisture content on the fracture behaviour of Norway spruce was investigated. The tensile strength rose to around 10% in samples with a lower moisture content. After reaching the maximum below the level of fibre saturation, it falls back, almost linearly. Irrespective of the moisture content, a rigid fracture behaviour was observed.