Increasing Wood Density Research Articles

Flame spread characteristics of densified wood with various sample widths and densities

Densified wood (DW) is a novel functional material with great mechanical properties, its structural characteristics make it attractive as an ideal building material for mid-to-high-rise timber constructions. However, its flame spread characteristics is not yet fully understood, which threatens its further developments and applications. This study experimentally and analytically investigates the impact of density and width on the flame spread behaviors and heat transfer characteristics of DW. Flame spread rate, mass loss rate (MLR), and flame height decrease with increasing wood density. Both MLR and flame height increase with the increasing width, while flame spread rate increases first and then decreases. Dimensionless power-law relationships among them were established, which well predict the measurements. The dominant gaseous heat transfer transits from radiation to convection with the increase of density. The critical density for this transition is increased with width. Both width and density impact the preheating length and total heat flux, which are combined to influence the flame spread rate. A dimensionless correlation among them was established with an R2 of 0.915 to the experiments of current and previous publications. This work helps to understand flame spread of DW and benefits the fire safety in timber construction.

Effect of chip thickness and tool wear on surface roughness and cutting power during up-milling wood of different density

The aim of this study was to determine the effect of average chip thickness and blade wear on the cutting power consumption and surface quality obtained in up-milling wood of different densities. The surface roughness was investigated using the contact method, recording the roughness parameters Ra and Rz, and the cutting power was determined using a wattmeter. The research was conducted for two variants of blade wear, i.e., sharp and blunt, and three variants of chip thickness (0.10, 0.06, and 0.02 mm). Four wood species with very different densities were tested, i.e., balsa (Ochroma pyramidale (Cav. ex Lam.) Urb.), obeche (Triplochiton scleroxylon K. Schum.), alder (Alnus glutinosa L. Gaertn.) and beech (Fagus sylvatica L.) For the lowest density woods, a better surface quality was found when cutting with a blunt knife compared to a sharp knife, while for the higher density woods (alder and beech) an inverse relationship was observed, i.e., a blunt knife resulted in increased surface roughness. For obeche wood, the surface roughness was dependent on the chip thickness. In addition, for low-density woods (balsa and obeche), no differences in cutting power were shown as a function of blade condition. It was shown that both an increase in wood density and chip thickness resulted in an increase in cutting power.

Impregnation Effect of Synthesized Fe3O4 Nanoparticles on the Jabon Wood’s Physical Properties

This study focused on characterizing synthetic magnetite (Fe3O4-NP) and evaluating the impregnated jabon wood’s physical properties. The co-precipitation method used for the synthesis of Fe3O4-NP, namely by mixing the iron solution (n/n Fe2+:Fe3+=1:2) with the strong base of sodium hydroxide (NaOH) (MG-S) and weak base of ammonium hydroxide (NH4OH) (MG-W) as precursors. The impregnation stage uses parameters of a -0.5 bar vacuum for half an hour and 2 bar pressure for 2 hours with magnetite concentrations of 1; 2.5; 5% w/v in a demineralized water solvent. Scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectrometry (FTIR) confirmed the presence of Ferrum content and Fe-O functional group in both Fe3O4-NPs produced. The Fe3O4-NP size was also measured via the X-ray diffraction analysis, namely 34.54 nm for the MG-S and 39.24 nm for the MG-W. Magnetic strength obtained was 7.51 mT for the MG-S and 8.58 mT for the MG-W. The impregnated jabon wood’s physical properties also improved with indications of an increase in wood density, weight percent gain (WPG), bulking effect (BE), anti-swelling efficiency (ASE), and a decrease in water absorption (WA). The results showed the best treatments were MG-S 2.5% and MG-W 5%.

Physico-Mechanical and Energy Properties of Pine (Pinus sylvestris) and Beech (Fagus sylvatica) Wood from Railroad Ties

The objective of the present work was to determine the physico-mechanical and energy properties of pine (Pinus sylvestris) and beech (Fagus sylvatica) wood from railroad ties. The ties were divided into internal and external parts as well as into parts impregnated and unimpregnated with creosote oil. The effects of creosote impregnation on wood hardness, compressive strength parallel to the grain, static bending strength, and calorific value were studied. The obtained results show that the parameters of the analyzed samples meet the standard requirements (EN 338) for construction wood (compressive and bending strength class: C50—pine; D70—beech). Depending on the particular property being studied, both pine and beech samples belong to the highest or one of the highest wood quality classes. Creosote oil considerably increased wood density (by 9% for beech and 19% for pine) but did not affect its hardness. Creosote impregnation significantly improved the compressive strength parallel to the grain of both wood species (beech: σc=51.99 MPa (IN); σc=57.78 MPa (OUT); pine: σc=36.56 MPa (IN); σc=42.45 MPa (OUT)); in the case of static bending strength, its value was increased for beech wood (σg=106.13 MPa (IN); σg=113.18 MPa (OUT)) and reduced for pine wood (σg=66.34 MPa (IN); σg=82.62 MPa (OUT)). The oil contained in wood from ties significantly elevated its calorific value (by 25% for beech and 10% for pine). Unfortunately, the presence of creosote oil currently prevents wood from railroad ties from being reused as the oil is deemed hazardous and carcinogenic. However, if it were possible to isolate the unimpregnated parts of railroad ties, they could be reapplied for construction or other uses.

Influences of Species and Density on the Horizontal Flame Spread Behavior of Densified Wood

Densified wood possesses outstanding mechanical properties and serves as a desired construction material for modern timber buildings. However, the limited research on its flame behavior hinders its broader applications. The authors of this paper experimentally and analytically investigated the influence of wood species and density on horizontal flame spread behavior. Densified oak and densified fir were tested. The flame spread rate decreased with wood density in both densified wood types. Their values were close at the same density. The mass loss rate (m˙) of the densified wood decreased with the increase in wood density. The densified oak had higher m˙ due to its lower lignin content. Dimensionless correlations between the m˙ and density were obtained which agree with the experiments. The flame heights (Lf) of the densified wood also decreased with the increase in wood density. The densified oak had higher Lf due to its higher m˙. As the densified wood density increased, the radiation (and conduction) was reduced (and enhanced), but the convection remained constant. The densified oak had lower convection, lower conduction, and higher radiation than the densified fir at the same density. Gas-phase heat transfer was dominant in the flame spread of the densified wood, but conduction was also significant as its contribution can be as high as 70% of gaseous heat transfer.

Wood Basic Density Assessment of Eucalyptus Genotypes Growing under Contrasting Water Availability Conditions

Limited research exists on wood properties in E. nitens × E. globulus hybrid genotypes grown in water-limited conditions generated by the climate change influence in Mediterranean areas. The EUCAHYDRO project aimed to assess environmental stress impacts on eucalyptus genotypes, including responses to reduced water availability, and to evaluate wood density and resistance using the non-destructive drill resistance technique. This study focused on 10-year-old E. nitens × E. globulus hybrids and Eucalyptus badjensis Beuzev. & Welch, revealing that low irrigation led to a 13% (p < 0.05) decrease in diameter and a 6.5% (p > 0.05) increase in wood density for the hybrids. On the contrary, E. badjensis demonstrated a noteworthy 22% increase in wood density (p < 0.05), while showing a corresponding 0.6% growth increase (p > 0.05), as measured by the diameter at breast height. Drill resistance measurement results indicated that E. nitens × E. globulus’ amplitude ranged from 20.1% to 26.6%, while E. badjensis’ ranged from 20.8% to 27.2%. The study revealed a high correlation between resistance amplitude and wood density, with coefficients of 0.97 observed for E. nitens × E. globulus and 0.84 for E. badjensis (p < 0.05). These findings fall within the range reported in similar studies involving Eucalyptus spp. The primary focus of the research was to assess the growth potential and wood quality of novel Eucalyptus spp. under conditions of water limitation. The study also explored the utility of drill resistance as a predictive measure for evaluating wood density as an indicator of wood quality.

Horizontal flame spread behavior of densified wood: Effect of structural characteristics

Densified wood (DW) is a recently developed material with excellent mechanical properties, considered as an ideal construction material for high-rise timber buildings. However, its flame spread behavior has not been well understood limiting its applications. This work for the first time experimentally and analytically investigates the horizontal flame spread behavior of DW. The influences of material structural characteristics (e.g. density) on heat transfer characteristics are focused. Thermally thin DW with density ranges of 441–1025 kg/m3 and a constant thickness of 2 mm were tested. The flame spread rate, mass loss rate (MLR) and flame height decreased with the increased wood density. A power-law correlation between the dimensionless MLR and dimensionless density is proposed, which well predicts the experiments with an R2 of 0.922. The increased wood density decreases flame height and reduces flame radiation. The gas-phase heat transfer shifts from radiation-dominant to convection-dominant. The longitudinal and radial thermal conductivities of DW increased with wood density. Empirical equations are optimized to predict the thermal conductivities of DW with R2 of 0.870 (longitudinal) and 0.837 (radial). The preheating zone length and the temperature gradient per unit length don’t vary significantly with wood density. Their values are averaged to 25.62 mm and 9.312 K/mm respectively. The longitudinal heat conduction is increased with the wood density due to the increased conductivity. However, this conduction increase is lower than the radiation decrease as the wood density increases. Thus, the total heat flux is slightly decreased with the wood density. The gas phase heat transfer dominates the flame spread. However, the longitudinal heat conduction can account for more than half of the gaseous heat transfer, and thus cannot be negligible. Results of this work improve the understanding of DW flame spread, which helps to evaluate the fire behaviors of timber construction.

Does climate change alter the nutrient trends of Cedrela fissilis Vell. trees in the southern Brazilian Amazon?

BackgroundThe increase in the frequency and intensity of droughts is pointed out as one of the main factors altering biogeochemical cycles in the Amazon basin. An eco-nutritional approach using X-ray fluorescence micro-analysis (µXRF) is proposed to verify the long- and short-term effects of droughts on the growth and xylem nutrient concentrations of Cedrela fissilis Vell.MethodsFourteen radii were selected from a tree-ring width chronology and X-rayed by Itrax Multiscanner. Profiles of ring width, wood density, and concentrations of aluminum (Al), phosphorus (P), sulfur (S), calcium (Ca), potassium (K), manganese (Mn), iron (Fe) and strontium (Sr) together with Al/Ca, Ca/Mn, K/Ca, Sr/Ca and Mn/S ratios were constructed and correlated with precipitation, temperature, the difference between precipitation and potential evapotranspiration (P-PET) and standardized precipitation–evapotranspiration index (SPEI).ResultsDuring dry years, C. fissilis showed narrower, less dense rings, lower Al, P, S and Ca, and higher K and Fe concentrations (the opposite was found in wet years). Ring width decreased (together with Al, P, S, K, Ca, Mn, Fe, Sr, Al/Ca, K/Ca and Sr/Ca) and wood density increased (together with Ca/Mn and Mn/S), which was associated with an increase in evapotranspiration and temperature over time, mainly since 1990. Cedrela fissilis showed a tendency to increase its capacity for resistance, and a recovery and resilience in growth over time associated with responses in Al, Ca, P and S. However, it showed a risk in the capacity for recovery of the pre-drought density values, associated with unsatisfactory responses in Al, Ca, K, Fe and P.ConclusionsThis study is the first attempt to analyze tree-ring nutritional evidences of C. fissilis trees to climate sensitivity and resilience to drought, based on long-term data from seasonal moist tropical forests of the Amazon. Our data suggested that C. fissilis is undergoing alterations in the concentration, use and redistribution of nutrients associated with increasing wood density and decreasing growth over time, due to the increase of drought frequency in the southern Amazon.

The Structural, Physical, and Mechanical Properties of Wood from Scots Pine (Pinus sylvestris L.) Affected by Scots Pine Blister Rust

The objective of this work was to examine the effects of Scots pine blister rust on the quality of Scots pine wood. The research material was taken from tree parts with visible symptoms of fungal infection as well as from unaffected tree parts. Our results show that the effects of the fungus Cronartium pini (Willd.) Jørst. are local and do not prevent the use of wood, and especially its unaffected fragments. Statistical analysis was used to describe the ways in which the pathogen altered wood. While the fungus statistically increased wood density, it significantly diminished its strength parameters. The structural properties of infected and healthy wood from affected trees were found to be similar and much higher than the average values for Scots pine. The higher transverse parameters of wood fibers had a beneficial effect on morphological properties. Scots pine blister rust significantly decreased wood homogeneity, which, together with stem deformation, lowered the quality of timber and reduced its yield.

RELATIONSHIP BETWEEN WOOD DENSITY AND ANATOMY WITH DRILLING RESISTANCE BY NON-DESTRUCTIVE EVALUATION METHOD

The Resistograph has emerged as efficient non-destructive evaluation method, because it allows the fast assessment of mechanical resistance, density and other wood properties. The aim of the present study is to assess the influence of wood density and anatomy on resistance to resistographi drilling. Twenty trees of Eucalyptus grandis x Eucalyptus urophylla hybrids, at the age group of 6 years, whose chest height discs (CHD) were removed and subjected to diametrical strip drilling, were herein assessed. The critical locations of amplitude radius were selected after the visual analysis of the resistogram; it was done to remove samples for the anatomical analysis and density carried out to determine several moisture contents. Resistance to drill increased due to increased wood density. Person’s correlation between resistance to drill and basic density reached 0.67; density in hygroscopic moisture was 0.65. There was moderate correlation between fiber wall amplitude and thickness (r=0.65). Cell wall thickness, fiber length and lumen diameter were the main anatomical features contributing to higher resistance to resistograph drilling.

Non-destructive Detection of an Invasive Drywood Termite, Cryptotermes brevis (Blattodea: Kalotermitidae), in Timber

Reliable drywood termite detection in structures is challenging but is critical for effective management. A microwave-based non-destructive method was evaluated for detecting termite activity. This study evaluated factors affecting the ability of this device to reliably detect Cryptotermes brevis in timber. The device displayed a high probability of successfully detecting C. brevis in naturally infested boards. The system detected termites 97% of the time when used at the highest sensitivity level, while producing few false positives. The number of termites did not affect detection ability, and detectable signals were produced even when a single termite was present. Detection success decreased with both increasing wood density and testing perpendicular to the grain in abrupt transition timber species. The device detected termites to a maximum depth of 45 mm in southern pine (Pinus spp.), but sensitivity declined with increased wood density with the detection limit declining to only 20 mm in denser Tasmanian oak (Eucalyptus spp). The device could only detect termites in samples with densities between 392 to 511 kg/m3 in 38 mm thick radiata pine samples. The results support the ability of microwaves to reliably detect C. brevis in timber.

Xylem anatomical traits determine the variation in wood density and water storage of plants in tropical semiarid climate

Wood density (WD) is a functional trait that integrates hydraulic safety and efficiency, water and carbohydrate storage, and biomechanical properties of plants. The global economic spectrum of wood shows that average WD tends to be higher in dry regions than in humid regions. In this study, we investigated the factors determining WD variation, the maximum water content in wood (WCmax), and their possibly consequences to hydraulic functioning of plants under tropical semiarid climate. Fourteen xylem anatomical traits related to mechanical support, water storage, and hydraulic efficiency and safety were measured in 39 woody species commonly found in a seasonally dry tropical forest in the Brazilian semiarid region. We tested the phylogenetic signal of all traits. The range of WD was 0.24–0.85 g cm−3 (average WD = 0.62 g cm−3). Fractions of vessel wall, fiber wall, fiber lumen, and fiber type highly influenced WD. Septate and gelatinous fibers decreased WD, whereas libriform fibers contributed to the increase in WD. Axial and radial parenchyma, fiber lumen fractions, and septate fibers presence determined WCmax variation. Xylem anatomical traits showed a weak phylogenetic signal. Wood density had a phylogenetic antisignal, indicating a functional convergence independent of phylogenetic proximity, despite species varying in their anatomical patterns. We conclude that the increase in the average WD in the analyzed species was associated with the investment in vessel wall, fiber wall fraction, and libriform fibers (mechanical support structures), which possibly increase hydraulic safety. Thus, we suggest that fiber types are important determinants of WD and WCmax and should receive more attention.

Impact of rotation length of Eucalyptus globulus Labill. on wood production, kraft pulping, and forest value

Most of the wood from Eucalyptus globulus Labill. plantations in Uruguay is harvested for pulp industry at an average age of 11 years. In this study we evaluated the volume and quality of the wood produced and the economic return for owners using different rotation length (from 6 to 13 years) and two different provenances (Jeeralang, Australia and Chivilingo, Chile) in experimental plots planted at two different sites (southwest and southeast of Uruguay). Silvicultural practices, industrial process, and economic aspects of the plantations were evaluated by measuring the following variables: survival, individual and per hectare growth, basic density, cellulose yield, wood consumption, cellulose production per hectare, dry solids content, fiber length, paper resistance, internal rate of return, and soil expectation value. The results showed that an increase in the harvest age generates: (i) an increase in the production of wood and cellulose per hectare at decreasing rates; (ii) an increase in wood density and yield; (iii) a reduction in the consumption of wood and solid contents in the cooking liquor; and (iv) a reduction in economic profitability at the farm level. No differences were found in the fiber length and resistance properties of the paper from wood harvested at different ages.

Insights about wood density in Atlantic Forest ecosystems: spatial variability and alternative measurement

Basic wood density (BWD) is a functional characteristic important to quantify carbon storage and is related to tree growth and its survival. We investigated BWD variability among tree species, populations, and forest types across the Atlantic Forest biome in Rio de Janeiro state, Brazil. We sampled and measured 576 trees of 83 species in 28 natural ecosystems in the Dense Ombrophilous Forest, Seasonal Semi-deciduous Forest, and the Restinga Forest. Stem wood from two different heights at each tree was acquired using a drill borer; discs were removed from branches in 20% of the height from 39 trees. BWD means increased from 0.42 for the most humid ecosystem to 0.675 g⋅cm−3 from the driest ecosystem. We identified changes in the wood as a result of climatic variables particular to different typologies, such as increased wood density in areas with lower precipitation and higher temperatures, were also observed within species, but with little difference in means. We identified three groups of species according to their BWD, different in mean height and diameter. The branches can be used to estimate tree wood density.

Variation of Selected Macrostructure Features and Density Wood of the European Spruce (Picea abies (L.) Karst.) in the Cross-Section of Trees over 90-Years-Old in Poland

In the present study, the following features were investigated: the variability of selected macrostructure features (width of the annual growth ring and share of latewood) and wood density of the European spruce (Picea abies (L.) Karst.) in a cross-section of the trunk. The study was conducted in locations of the northeastern range (12 research plots) and the southwestern range (20 research plots) of spruce in Poland. On the testing plots, Pressler drill borehole samples were taken from 15 selected trees. Then, the borehole samples were divided into 2 cm long sections and, for each section, the average width of the annual growth ring, the average share of latewood, and the relative wood density were calculated. In conclusion, it was found that the width of the annual growth rings in the tested material was increasing constantly from the outer circumference (the perimeter) of the trunk towards the pith. The greatest share of latewood was found not only in the perimeter zones of the tree trunk but also in the zones close to the pith. It was also discovered that the highest wood densities occur in the perimeter zones, and that these densities decrease towards the pith. It was only in the sections next to the pith that an increase in wood density was noted. Having analysed the relationships between the examined features, it can be concluded that the width of annual growth rings affects both the share of latewood and the wood density. The aforementioned were negative correlations, whereas the increase in the share of latewood also impacts the increase in wood density and was determined to have a positive correlation.

Variation in Growth, Wood Density, and Stem Taper Along the Stem in Self-Thinning Stands of Sassafras tzumu.

Silvicultural practices greatly improve the economic value of wood products from forests. Stem dimensions, wood density, and stem form are closely linked to end-product performance. This research aimed to examine the effects of stand density and stem height on variables that reflect ring growth and wood properties of Sassafras tzumu stands during the self-thinning phase. Between the ages of 10 and 40 years, the number of stems per hectare has declined from 1,068 to 964 due to density-dependent mortality. As the relative stand density decreased, there were significant reductions in the average tree ring width (5.07–3.51 mm) and increases in latewood proportions (49.88–53.49%) and the density of the annual growth ring (165.60–708.58 kg/m3). Therefore, ring density, earlywood density, and latewood density increased with decreasing relative stand density after self-thinning occurred. Ring width, earlywood width, and latewood width significantly increased from the base to the apex of the stem. Stand density and stem height had additive effects on S. tzumu wood properties during the self-thinning phase. A shift in the growth allocation along the longitudinal stem in response to self-thinning resulted in decreasing radial growth, increasing wood density, and improved stem form. In summary, we found a significant influence of stand density on tree ring growth, wood quality, and stem form of S. tzumu trees during the self-thinning phase.

Emission of CO2 and CH4 From 13 Deadwood Tree Species Is Linked to Tree Species Identity and Management Intensity in Forest and Grassland Habitats

AbstractDeadwood is an important component of the global carbon cycle, and its decomposition releases carbon dioxide (CO2) and methane (CH4) into the atmosphere. However, the main drivers of these greenhouse gas emissions from deadwood are not well understood. We investigated drivers that govern the CO2 and CH4 emission rates of 793 deadwood specimens from 13 different tree species, which were exposed on 27 forest and 38 grassland plots at Schorfheide‐Chorin (Germany) for one year. Tree species identity was an important driver for emissions of both gases, whereas habitat type and management intensity were only important for CO2 emission rate. CO2 emission rates were positively linked to mass loss and were one‐third higher in forest compared to grassland habitats. The wood traits organic extractives, lignin, and sulfur content were negatively associated with CO2 emission rates, whereas carbon, nitrogen, and magnesium content showed the opposite effect. Among climate variables, air humidity in forest and soil moisture in grassland habitats positively affected CO2 emission rates. CH4 emission rates showed a negative relationship with increasing wood density exposed in both habitat types but were positively related to tree species with higher sulfur contents. Taken together, CO2 emission rates from deadwood were well predicted by wood traits, management intensity and climatic variables, whereas CH4 emission rates were less well predictable and were influenced only by wood traits that differed from those of CO2 emissions. Our results provide a deeper insight into the mineralization processes of deadwood and should be considered in further carbon cycle assessments.

Assessment of Indirect Charring in Doweled Wood Connections and External Steel Plates Submitted to Fire

AbstractThe present work aims to evaluate the wood connections, with dowels and external steel plates, in double shear, subjected to fire. The presence of external steel plates, in a fire situation, leads to a non‐uniform distribution of charring in the internal wooden elements. Based on the results, it is observed that the charring rate in wood does not remain constant and increases with the time of fire exposure of the steel elements. However, based on the influence of other variables, the charring rate decreases with increasing dowel diameter and with increasing wood density.

Performance of Densified Wood Glulam as Building Bio-Material

In this research, some practical aspects of densified wood glulam were investigated. For this aim, poplar wood specimens were densified by hygro-thermo-mechanical technique. Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin. Physical and mechanical properties of glulams were investigated according to ASTM D 143-09, ASTM D 905-03 and ISO 8375 standards. Based on obtained results, using this process (steam and pressurize compaction) resulted in improvement of physical and mechanical properties of glulam specimens. Optical microscopic and scanning electron microscopic (SEM) pictures were proved structural changes on wood material during of applied technique. Generally, the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability. This technique showed a significant effect on water absorption; the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter. Also, delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination. Moreover , modulus of rupture, modulus of elasticity, shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time. Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.

Effects of an innovative densification process on mechanical and physical properties of beech and Norway spruce veneers

Increased wood density is obtained by compressing the wood porous structure under suitable moisture and temperature conditions to improve its physical, mechanical and color properties. A recently proposed wood densification method based on partial removal of lignin and hemicellulose in hot water solution of sodium hydroxide and sodium sulphite has shown promising results on solid wood. However, its applicability and effect on thin wood veneers have not been tested yet. In this study, the timing of the method has been adapted to estimate the densification treatment intensity dependence of wood properties (wood density and modulus of elasticity) and color change of softwood (Norway spruce) and hardwood (beech) veneers. Compared to control, density and rigidity increased, with improved wood properties peaking after only 90 s of treatment intensity. Furthermore, the color became darker after treatment compared to control, with no significant color difference between treatment intensities. In conclusion, densification of veneers, according to the presented adapted method, provides a significant improvement of veneers physical and mechanical properties, and produces color changes perceptible by the human eye. Our results can be further implemented and adapted to application in industrial plants, calling for new application of densified veneers.