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This paper presents numerical modelling of the ballistic impact response of hybrid laminated structures, which are developed through combinations of ceramics, Ultra-High-Molecular-Weight Polyethylene (UHMWPE), Kevlar and compressed wood. It is, for the first time, to embed the compressed wood in the ballistic panel and numerically investigate the impact response of the hybrid structures made of the multiple constituent materials. Different constitutive models and the related failure criteria were employed in the modelling to capture the ballistic responses of the constituent materials and hybrid structures. The numerical simulations were compared with the corresponding experimental results with acceptable correlation. The essential features of the hybrid composite structures subjected to high velocity impact were simulated by the finite element (FE) models, such as deformation and failure modes, back-face signature and the residual velocities. The FE models developed are ready to be used to assist design lightweight composite armour with optimized ballistic resistance and self-weight.

Building with cross laminated timber (CLT) has gain increased interest over the last years, but in common to other wood-based building systems, inadequate low-frequency sound insulation is seen as a problem. This paper deals with two methods to improve the sound insulation of CLT panels, normally made from spruce: 1) heavy CLT, introducing compressed, i.e. densified, spruce as well as alternative wood species, and 2) elastic layer based upon shear motion. In addition to a series of laboratory measurements, a full-scale CLT floor made of two 60 mm birch panels with a 12 mm elastic layer in between was tested in a two-room test mock-up. The results from the acoustical measurements showed that the floor has about 7 dB greater airborne and impact sound insulation for one-third octave bands, 50–3150 Hz, compared to a standard CLT floor of the same total height.

This paper reports on multiple stage bleaching and its effect on the mechanical and swelling properties of compressed wood (CW). The natural wood specimen was bleached with NaClO2 in five steps and three hot-pressing conditions. Their effects were investigated in morphologies: lignin content, alpha-cellulose content, compression ratio, mechanical properties, swelling and, water contact angle. After compression, the wood specimens became dense and the most porous structures collapsed. The lignin content decreased as the bleaching steps progressed, and the highest alpha-cellulose content was observed at the third bleaching step. This CW showed the best mechanical properties: bending strength was 240.1 ± 35.7 MPa, and Young's modulus was 23.08 ± 0.89 Gpa. The CW swelling decreased as the bleaching step progressed, and was associated with the density decrease and the compression ratio increase with the bleaching step. The B3 is an optimum bleaching step that accounts for the best mechanical properties, which might be associated with the highest alpha-cellulose content. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is an innovative wood product that can be used to build midrise and tall wood construction as an alternative to concrete, masonry, and steel. As floor, roof, and wall made of CLT is subjected to out-of-plane bending, rolling shear (RS) failure of cross-layers can arise prior to bending failure of the outermost layers, which governs the load-carrying capacity of CLT. In fact, the global deflections of CLT depend on the rolling shear modulus of cross-layers, which is much lower than shear modulus parallel to grain. Therefore, it is necessary to determine and improve the rolling shear strength and modulus of cross-layers. In this paper, several test methods were firstly summarized, after which the main influence factors on rolling shear properties were reviewed. Finally, seven configurations of hybrid CLT with three layers were tested to assess the rolling shear properties of hybrid CLT, in which the outer layers are made of Spruce-Pine-Fir (SPF) and the cross-layer is made of different materials such as birch, compressed wood (CW), laminated veneer lumber (LVL), Parallel strand lumber (PSL), plywood, oriented strand board (OSB), and glued laminated bamboo (GLB). The CLT made of SPF was also tested, whose rolling shear properties were regarded as reference. The rolling shear properties of GLB are about twice as high as those of SPF. Other materials do not exhibit superior rolling shear properties to SPF. The compressed wood shows a significant ductility in rolling shear failure. [ABSTRACT FROM AUTHOR]

The objective of the research was to densify wood of Cupressus lindleyi, Cedrela odorata, Swietenia macrophylla, Tabebuia donnellsmithii, Fraxinus uhdei, Fagus mexicana, Dalbergia paloescrito and Guazuma ulmifolia. The densification of the wood increases its apparent density, its wave speed and its dynamic modulus; to verify this, before and after the procedure, measurements of these values were taken. This artificial increase in the apparent density of the wood and the consequent increase in its dynamic modulus can mean a technological gain in the transformation and modification of the intrinsic properties of this material. The eight woods investigated are potentially candidates for densified treatment. [ABSTRACT FROM AUTHOR]

Mechanical densification treatments make it possible to increase the density of low- or moderate-density woods, and thus a high mechanical strength of densified wood and high-value products can be obtained. The authors' previous treatments showed that the diffusion and distribution of steam and the release of vapor inside densified wood were prevented to some extent during thermo-hydro-mechanical (THM) densification, causing the occurrence of protrusions, carbonization, blisters, and blows. This study aimed to overcome these problems. Based on the authors' previous THM densification, different materials, such as fabric, metal mesh, metal foam, and sintered metal mesh laminate (SMML), were used to improve the process. Densification was tested on different wood species. The results showed that SMML was the preferable material for THM densification through enhancing diffusion and distribution of steam, and evaporation of moisture inside wood. No protrusion, carbonization, blisters, or blows were found after densification with SMMLs. The densified wood specimens showed uniform color and a neat surface. [ABSTRACT FROM AUTHOR]

The recovery behavior and selected mechanical properties were studied for Populus tomentosa wood subjected to surface compression followed by heat treatment. The surface compression of wood was carried out in an open hot-pressing system at 180 °C with compressed thickness of 2 to 18 mm. The surface-compressed wood was treated by atmospheric heat treatment or 0.30 MPa pressurized superheated-steam heat treatment at 180 °C for 2 h. The results showed that the set recovery of compressed wood decreased with increasing compressed thickness before posttreatment. Atmospheric and pressurized heat treatment reduced the average set recovery of compressed wood significantly from 12.9% to 4.1% and 1.5% respectively, after conditioning at 40 °C and 90% relative humidity. Moreover, mechanical properties including the modulus of elasticity (MOE), modulus of rupture (MOR), hardness, and surface hardness increased with elevating compressed thickness. Both atmospheric and pressurized heat treatment reduced the MOR, hardness, and surface hardness of compressed wood. Analysis of variance showed that the effects of heat treatment on mechanical properties was not significant, except pressurized heat treatment decreased hardness significantly. With a compressed thickness of 10 mm, MOE, MOR, hardness and surface hardness were increased by 52.6%, 36.4%, 122.0% and 129.6%, respectively, compared with untreated wood. [ABSTRACT FROM AUTHOR]

To expand the applications of low-density wood, solid white poplar (Populus tomentosa) wood with a moisture content of 10.6% was compressed 5 mm radially at 90 °C, 120 °C, 150 °C, 180 °C, and 210 °C, and the density profile characteristics were analyzed. It was found that compressed wood with a non-uniform density profile contributed to the peak density and average density of the compressed layer, where the highest values were 0.87 g/cm3 and 0.72 g/cm3, respectively. The density peak and compressed layer were formed at various distances from the wood surface according to the pressing temperatures tested. It was concluded that the pressing temperature had a great effect on the density profile of the compressed wood and the pressing temperature effectively controlled the shape of the density profile. [ABSTRACT FROM AUTHOR]

Since human creation up to now, wood has been discussed as an important organic material, therefore its maintain and optimum usage is a considerable problem. From one hand, with due attention to condition of forest in Iran, using fast growing specie Paulownia provides new way in wood industries. But from other hand, this specie with low density has low strength. One of the suggested ways to increase density of this wood is its impregnation by resin and to compress it. In this research it is tried to increase the penetrability and impregnation of Paulownia by using urea formaldehyde resin at first pretreatment and then compression should be done. In order to perform this process, two variables pretreatment and compression percent were defined that each of them had two levels. The pretreatment was performed by NaCl and NaOH and 40, 50% compression. Totally, 72 samples were prepared and after producing the compressed wood, the absorption percent and mechanical properties were evaluated which included compression parallel to grain, modulus of rupture, modulus of elasticity in bending and impact strength. The results showed that the provided mechanical properties and pretreatments samples with NaCl had most values of these properties in 40 and 50% compression levels.

Copyright of Acta Silvatica et Lignaria Hungarica is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Finite element models were, in the first time, developed to simulate the pre-stressing behaviour of Glulam beams with insertion of compressed wood blocks, which were further used to simulate the structural behaviour of the pre-stressed beams subjected to subsequent destructive bending. Here, both the Glulam and compressed wood were modelled as orthotropic elasto-viscoplastic materials. The moisture-dependent, including spring back, swelling of the compressed wood block and the creep of the Glulam were considered in the modelling. The models developed were validated against the corresponding experimental results, with reasonably good correlation in terms of the free swelling, the precamber, initial stress state of the Glulam beams reinforced and load-deflection relationships. With validated models, further studies were then undertaken to investigate effects of the thickness, depth and spacing of compressed wood blocks on the precamber, initial bending stiffness and ultimate load carrying capacity of the beams pre-stressed. The results indicate that there are significant enhancements on the precamber (up to 1/288 of the deflection/span ratio), the initial bending stiffness (up to 23.8%) and the ultimate load carrying capacity (up to 10.4%). [ABSTRACT FROM AUTHOR]

Oil palm trunks are a by-product of oil palm plantations and provide raw material to the woodworking industries. However, their resistance against degradation by termites needs to be improved; this study investigated hot pressing as a chemical-free method to improve resistance. The main objective was to assess resistance to termites conferred to oil palm wood by hot pressing at various temperatures (140, 180, and 220 °C) for a fixed duration of 8 min and maximum pressure of 2 MPa. The samples were the only available nutrition to subterranean termites (Coptotermes gestroi Wasmann) in a 4-week no-choice test. The thermally compressed oil palm wood did not show any significant effect of the pressing temperature on mass loss, but the surface damage to the samples with treatment at 220 °C indicated improved resistance to subterranean termites based on visual observation.

Compressed wood, which is formed by a process that increases the wood’s density, aims to improve its strength and dimensional stability. Compressed wood can be used in building and construction, especially for construction of walls and flooring. Currently, supplies of wood are becoming limited, and the oil palm tree has become one of the largest plantation species in Malaysia. Oil palm trunk could be an appropriate choice for an alternative source for compressed wood. This paper aims to review the current status of oil palm biomass, including the availability of this tree, in order to illustrate the potential of oil palm biomass as an alternative source for compressed wood. Up to the present there has been insufficient information regarding the manufacturing conditions and properties of compressed wood from oil palm trunk. This paper will cover the background of compressed wood and the possibilities of producing compressed wood using oil palm trunk as a raw material.

A new approach to strengthen glulam beams by using compressed wood was introduced by author. Compressed wood (CW) is made of a lower grade wood, which is densified in the radial direction under specific pressure and temperature conditions. In order to optimize the structural performance of glulam beams reinforced by compressed wood, in terms of load carrying capacity, strength and stiffness, parametric studies were carried out on thickness, depth and space of CW blocks. In this study, the dimensions of the beam models were 3800 mm in length, 120 mm in width and 200 mm in depth which comply with the requirements from Eurocode 5, and BS EN 408:2003, where the ratio between the span and the depth equals to 18. There are nineteen beams simulated in the parametric studies using validated FE models. The parameters covered in the simulations include the thickness, depth and spacing of CW blocks, however the CW block width and beam dimensions were remained unchanged. The results indicate that there are significant enhancements on the pre-camber (up to 1/288-deflection/span ratio), initial bending stiffness (up to 23.84%) for a beam reinforced by seven CW blocks with a thickness and depth of 50 mm and 95 mm respectively and ultimate load (increased to 10.4%) of glulam beams reinforced by seven CW blocks with thickness of 40 mm. [ABSTRACT FROM AUTHOR]

This paper explores changes in the quality of the surface of aspen wood after pressing. Pressing, a type of processing, facilitates changes in surface quality and smoothness, thereby producing wood suitable for the furniture industry. The results obtained for the pressed wood surface were compared with those obtained for wood surfaces that were not subjected to pressing. Attention was paid to the impact of moisture, the degree of compression, and plasticizing by steam. The change in smoothness/roughness was monitored in both the longitudinal and transverse directions (relative to the grain). The contact method was used to measure the roughness both before and after pressing. The independent variables of moisture content and degree of compression had the greatest impact on the smoothness/roughness. Plasticizing by steam had no greater impact. Therefore, the non-plasticized aspen wood was determined to be more suitable for the given purpose. [ABSTRACT FROM AUTHOR]

The objective of this research was to determine the influence of wood species (Fagus sylvatica L. and Populus tremula L.), thickness (4, 6, 10, 18 mm), and degree of densification (0%, 10%, and 20%) on the impact bending strength (IBS) and Brinell hardness (BH) in the radial direction. Three-factor analysis of variance confirmed that the difference in IBS was significantly related to the wood species and wood thickness. Wood densification did not have a significant effect on IBS. In addition, beech wood exhibited higher IBS values than aspen wood. The IBS values increased proportionally with increasing thickness. All factors affecting Brinell hardness were statistically significant, although thickness had the smallest influence overall. The Brinell hardness values were substantially higher in beech wood than aspen wood, and in some cases were more than three times greater. On the other hand, densification exhibited a more positive effect on increasing Brinell hardness for aspen wood than beech wood. [ABSTRACT FROM AUTHOR]

Hygrothermal recovery (HTR), the dimensional changes in wood induced by hygrothermal treatment, was investigated using both compression and normal wood of sugi ( Cryptomeria japonica). The elastic released strain of growth stress was measured on living tree surfaces; subsequently, the specimens were taken from the same position to measure HTR. HTR was measured as dimensional changes due to treatment at 20, 40, 60, 80, and 100 °C in hot water ranging from 200 min to 177 days. The intensity of HTR had a positive relationship with elastic released strain of growth stress. This result suggests that HTR is the relaxation of the viscoelastic component of growth stress accumulated during the maturation process of trees. The rate of HTR clearly showed a time-temperature dependency: higher at higher treatment temperatures and lower at lower treatment temperatures. Based on kinetic analysis, the apparent activation energy ( E) was calculated as 407 kJ/mol, which is similar to the published E of lignin softening implying that the HTR is a lignin-related phenomenon. [ABSTRACT FROM AUTHOR]

Dimensional changes in both non-densified and densified, thin, wooden components and layered materials after external pressing forces were released were evaluated in this work. Densification was carried out using a cold process on a semi-automatic hydraulic pressing machine. The specimens' dimensional stabilities, focusing mainly on their residual plastic deformations, were monitored. The impacts of several factors, such as wood species, material thickness, densification degree, and their combinations, were analyzed. Results showed that, with increased degree of densification, the relative plastic deformations (pressing degree) usually decreased. With regard to the compositions explored, the best combination was a top poplar layer densified by 10% plus a bottom beech layer densified by 20%. The impacts of each of the factors on the pressing degree values proved to be significant; the least significant was the bottom beech layer thickness and degree of densification. The greatest practical benefits can be obtained using the recommended combinations of composite layers. [ABSTRACT FROM AUTHOR]

A new approach to reinforce glulam timber beams using compressed wood (CW) has been developed by the Author. The compressed wood blocks are inserted into pre-cut holes on the top of glulam beams to produce pre-camber and to generate initial tensile and compressive stresses on the top and on the bottom extreme fiber of the glulam beam, respectively. A simple analytical approach has been developed to predict pre-camber deflections of the beams reinforced with three CW blocks. Assuming that moisture-dependent expansion of the CW block creates an interactive linear pressure between the glulam beam and the CW block, this would generate a pair of eccentric force away from the neutral axis of the beam. It is shown that the pre-camber deflection predicted at midspan of the short beams with various reinforcing arrangements give good agreement with the measured pre-camber from previous experimental results. [ABSTRACT FROM AUTHOR]

Scots pine ( Pinus sylvestris L.) wood was surface densified in its radial direction in an open press with one heated plate to obtain a higher density on the wood surface whilst retaining the overall thickness of the sample. This study investigated the effect of temperature (100, 150 and 200 °C) and press closing speed (5, 10 and 30 mm/min, giving closing times of 60, 30 and 10 s, respectively) on the micromorphology of the cell-wall, as well as changes occurring during set-recovery of the densified wood. The micromorphology was analysed using scanning electron microscopy (SEM) combined with a sample preparation technique based on ultraviolet-excimer laser ablation. Furthermore, the density profiles of the samples were measured. Low press temperature (100 °C) and short closing time (10 s) resulted in more deformation through the whole thickness, whilst increasing the temperature (150 and 200 °C) and prolonging the closing time (30 and 60 s) enabled more targeted deformation closer to the heated plate. The deformation occurred in the earlywood regions as curling and twisting of the radial cell-walls, however, no apparent cell-wall disruption or internal fracture was observed, even at low temperatures and fast press closing speed, nor after soaking and drying of the samples. In the SEM-analysis after soaking and drying, it was noticed that the cells did not completely recover their original form. Thus, part of the deformation was considered permanent perhaps due to viscoelastic flow and plastic deformation of the cell-wall components. [ABSTRACT FROM AUTHOR]

Oil palm trunks are a by-product of oil palm plantations and provide raw material to the woodworking industries. However, their resistance against degradation by termites needs to be improved; this study investigated hot pressing as a chemical-free method to improve resistance. The main objective was to assess resistance to termites conferred to oil palm wood by hot pressing at various temperatures (140, 180, and 220 °C) for a fixed duration of 8 min and maximum pressure of 2 MPa. The samples were the only available nutrition to subterranean termites (Coptotermes gestroi Wasmann) in a 4-week no-choice test. The thermally compressed oil palm wood did not show any significant effect of the pressing temperature on mass loss, but the surface damage to the samples with treatment at 220 °C indicated improved resistance to subterranean termites based on visual observation. [ABSTRACT FROM AUTHOR]

Oil heat treatment can effectively improve the dimensional stability and bio-durability of wood. However, the characteristics of high oil uptake (50 percent or higher) and high susceptibility to leaching from wood have an adverse effect on subsequent manufacturing processes of wood product and production costs. A solvent extraction (100% ethanol) process was used to extract the surplus oil from the treated wood. Because the making of powder specimens from high oil uptake wood would result in experimental error, a new method of determination of oil uptake percentage was proposed by two step Soxhlet extraction with ethanol. The oil uptake percentage of oil-heat-treated poplar wood at 180 oC for 2 h with this method was determined to be 113.29%. Additionally, the average oil uptake percentage (OUP) of oil-treated poplar after the oil extraction process for 2 and 6 h was 54.82% and 29.11%, respectively. Moreover, the average oil extraction percentage (OEP) of specimens with the oil extraction process at the first step (wood sticks) in the Soxhlet extractor apparatus was larger than that of oil-heat-treated poplar specimens. Due to the combined effect of chemical changes in the wood at high temperatures and of oil uptake by the wood, the compression strength parallel to the grain changed at different OUP levels. [ABSTRACT FROM AUTHOR]

Thermo-hydro-mechanical densified balsam fir ( Abies balsamea (L.) Mill.) wood used in this study was made by compressing wood in the radial (R) direction (ray direction) at a temperature of 230 °C and a compression ratio of 60 % for 20 min, which significantly increased its density and some mechanical properties. However, the elastic parameters of densified wood in the R and tangential (T) directions, [moduli of elasticity ( E and E), shear modulus ( G), and Poisson's ratios ( μ and μ)], have seldom been reported because of the relatively small thickness of a densified wood specimen. This study measured the E, E, G, μ, and μ of densified balsam fir wood using a digital image correlation method, which was used to measure the strain field of a specimen under compressive loading. The corresponding five elastic parameters of undensified balsam fir wood were also measured. The experimental results were: (1) E was 284 MPa, which was about 66 % lower than that of undensified fir; (2) E was 2551 MPa, which was about ten times larger than that of undensified fir; (3) G was 21 MPa, which was about 50 % lower than that of undensified fir; and (4) μ and μ were 0.104 and 0.331, which were about 75 and 10 % lower than those of undensified fir, respectively. [ABSTRACT FROM AUTHOR]

The interactive effect of the thermo-mechanical densification and heat treatment on the set-recovery of modified wood were investigated for optimizing the combined modification process in this study. Process parameters such as thermo-mechanical densification temperature, duration of densification, and heat treatment temperature were selected as main factors. Three levels of each of these factors were chosen, and then nine experiments plus one verification experiment were conducted according to the principles of the Taguchi DoE method and the results of ANOVA analysis. It was observed that the dimensional stability of combined modified Chinese fir wood in the compression direction can be effectively improved by elevating the heat treatment temperature and densification temperature, the percentage contributions of which were 76.04% and 21.18%, respectively. Meanwhile, the set-recovery had no dependence on the duration of the densification process. The value of the set-recovery in the verification experiment agreed quite well with the predictions. From an economic view, the optimal condition for the combination modification of Chinese fir wood was that of a densification temperature of 170 °C, densification duration of 10 min, and heat treatment temperature of 200 °C. [ABSTRACT FROM AUTHOR]

Surface densification is a process by which the mechanical properties of the wood surface can be improved, increasing the attractiveness of low density wood for applications such as flooring. The purpose of this study was to investigate the development of undesired cupping deformations in surface densified solid wood. The effects of process parameters (compression ratio, temperature, holding time, closing time, and initial moisture content) on cupping were studied, and correlation analysis was used to determine the strength of association. Correlation analysis was also performed to explore the potential dependence of cupping on the density profile characteristics of surface densified wood. Correlations of moderate strength were found between cupping and the process parameters, as well as between cupping and the density profile characteristics. Compression ratio was found to be the most influential process parameter: samples with a high compression ratio showed distinctly different cupping behaviour than samples with a low compression ratio. Density profile characteristics were considered a probable contributor to cupping, but the influence of other effects was also considered likely. Interestingly, certain combinations of parameters were found to result in very small cupping deformations. Therefore, the results of this study indicate that cupping can be minimised by optimisation of process parameters. [ABSTRACT FROM AUTHOR]

Compressed lumber is considered to be a superior structural material due to its uniform properties and higher strength than other solid timbers. This study presents the effect of steaming on some properties of compressed lumber of oil palm (Elaeis guineensis) trunks (OPT). The specimens were steamed at a temperature of 130 °C for 2 hours before being compressed in a hot press and evaluated for their physical and mechanical properties. Compressed OPT without steaming was used as a comparison sample to compare the effect of steaming on compressed OPT. The average modulus of rupture of steamed compressed OPT samples was 31.36 MPa, which was 8.7% higher than the compressed OPT without steaming samples. The modulus of elasticity was determined to be 8919 MPa, 9.9% higher than the compressed OPT samples. Steaming enhanced the dimensional properties of the samples. Thickness swelling and water absorption of the steamed compressed OPT samples were 6.57% and 33.84%, respectively, lower than those of the samples without steaming. Some other properties such as compression strength, dynamic bending strength, and the compression and recovery ratios were also evaluated. Scanning electron micrographs taken from the cross section of the samples showed a clear difference between the compressed and uncompressed oil palm. [ABSTRACT FROM AUTHOR]

Solid Scots pine ( Pinus sylvestris L.) wood was surface densified to three different degrees of compression and hydrothermal post-treatment after surface densification process was performed. The study determined the significance of degree of compression and hydrothermal post-treatment on the density profile generated and the resulting improved Brinell hardness. It was found that different degree of compression resulted in only slightly different density profiles, when compared on the absolute thickness scale. Although the hydrothermal post-treatment lead to an average mass loss of 3.8 % in surface densified specimens regardless of the degree of compression, density profile of surface densified specimens was not significantly affected by hydrothermal post-treatment. Furthermore, the surface densification increased the Brinell hardness more than 90 %. Degree of compression had limited effect, which means that it did not matter if the specimens were compressed from 22 to 15 mm or 18 to 15 mm, the Brinell hardness was approximately the same. The hydrothermal post-treatment did not reduce the Brinell hardness of control and surface densified specimens. Furthermore, the surface densification significantly increased the elastic recovery of surface densified wood, which was measured during hardness measurements and was affected by degree of compression. Additionally, the hydrothermal post-treatment reduced the elastic recovery, in control specimens and surface densified specimens. [ABSTRACT FROM AUTHOR]

Compressed wood, which is formed by a process that increases the wood's density, aims to improve its strength and dimensional stability. Compressed wood can be used in building and construction, especially for construction of walls and flooring. Currently, supplies of wood are becoming limited, and the oil palm tree has become one of the largest plantation species in Malaysia. Oil palm trunk could be an appropriate choice for an alternative source for compressed wood. This paper aims to review the current status of oil palm biomass, including the availability of this tree, in order to illustrate the potential of oil palm biomass as an alternative source for compressed wood. Up to the present there has been insufficient information regarding the manufacturing conditions and properties of compressed wood from oil palm trunk. This paper will cover the background of compressed wood and the possibilities of producing compressed wood using oil palm trunk as a raw material. [ABSTRACT FROM AUTHOR]

The water vapour sorption behaviour of Scots pine ( Pinus sylvestris L.) and Scots pine that was densified, thermally-modified, or subjected to a combination of thermal modification and densification has been investigated. It was found that all modifications resulted in a decrease in the equilibrium moisture content of the wood samples throughout the hygroscopic range. The water vapour sorption isotherms were reproducible for the unmodified wood samples, but changed between the first and subsequent sorption cycles for the densified, thermally-modified and for wood subjected to a combination of the two treatments. This is the first time that changes in the sorption isotherm between the first and subsequent cycles have been reported for thermally-modified wood. Irrespective of the wood treatment the difference between the adsorption and desorption isotherm loops (sorption hysteresis) was the same and greater than that observed for the unmodified wood sample. After the first sorption cycle, the hysteresis decreased to the values observed for the unmodified wood, even though the isotherms were different. The sorption kinetic behaviour was also investigated and found to be accurately described using the parallel exponential kinetics (PEK) model. The PEK model describes the dynamic sorption behaviour in terms of a fast and slow kinetic process and this has been interpreted in terms of two Kelvin-Voigt elements coupled in series (i.e. relaxation-limited kinetics). [ABSTRACT FROM AUTHOR]

This study evaluated the significance of different process parameters (press temperature, closing time, holding time, moisture content and compression ratio) on solid wood surface densification and its effect on the density profile generated in Scots pine sapwood. Changes in the microstructure of the wood were also evaluated microscopically. The results showed that with a shorter closing time, densification occurred closer to the sample surface than with an extended closing time. At a compression temperature of 150 °C, the vertical density profile exhibited a sharp peak in density that was close to the wood surface. A higher temperature of 200 °C resulted in a slightly broader density peak that was less intense and further from the surface. A holding time of 10 min resulted in the wood compressing to a slightly greater extent than when using a holding time of 1 min. Higher moisture content led to more extensive deformation. The results indicate that surface modification by densification is a viable method of enhancing wood properties. [ABSTRACT FROM AUTHOR]

Abstract: In seeking an efficient method for drying very wet chips, we developed and tested an original continuous dewatering system using mechanical compression (10–30MPa). The moisture content of cedar chips decreased from 100–270% to 85–130% (dry basis), and the energy required to remove the water was 9% (power consumption basis) and 25% (primary energy basis) for heat energy to evaporate the water. In the case of combined drying, in which roller compression was applied first, followed by thermal drying, the energy required to dry wet cedar chips to a moisture content as low as 20% was 49% (power consumption basis) and 58% (primary energy basis) of that required for thermal heating alone. These results indicate that the combined method uses less energy to dry very wet wood chips. [Copyright &y& Elsevier]

Compressed wooden plates and dowels were used to connect members in post-and-beam structures as a substitute for a steel fastener. In order to take advantage of the characteristic properties of compressed wood and to achieve optimum joint performance, two compressed wooden plates were used in each joint to give multiple shear planes for each compressed wooden dowel. Consequently, this type of joint showed very good properties in pull-out and momentrotation performance, and its engineering design could be further optimized. This joint is expected to be introduced to many kinds of structural systems, including long-span frame structures made of domestic timber found in Japanese residential houses. [ABSTRACT FROM AUTHOR]

• Design hybrid ballistic panels with ceramic, Kevlar, Dyneema and compressed wood. • Ballistic impact tests on hybrid composite laminated panels. • Investigation of failure modes and back face signature. • Development of analytical models to predict ballistic performance. • Provide useful data to assist design of ballistic structures. Classic lightweight composite armour systems are usually made of ceramics, metals and fabric laminates separately or combination of two materials to resist a ballistic impact by 7.62 mm projectile. To enhance the ballistic impact resistance, this paper proposes hybrid laminated structures, which are developed through combinations of ceramics, Dyneema, Kevlar and compressed wood. There were twenty-five hybrid ballistic panels manufactured first, which were then subjected to field ballistic tests with 7.62 mm (×39 mm) bullets in a velocity range from 806.0 to 887.5 m/s. Here, five of twenty-five panels successfully stopped 7.62 mm projectile. The results of the ballistic performance, energy absorption, back face signature and failure mode of each type of the composite panels were obtained and examined. The mechanisms of ballistic resistance associated with different hybrid panels designed are investigated and discussed. In addition, analytical models are developed to predict ballistic perforation performance of single material layers and the related hybrid composite structures. The theoretical predictions of residual velocities are compared with the corresponding experimental measurements in a good agreement. These results provide the first-hand data to support further concept design of the hybrid ballistic panels and to validate computer models for optimizing lightweight composite armour. [ABSTRACT FROM AUTHOR]

The wood pressed constitutes a correct selection for a wide range of applications at the construction. This work discuss the possibilities of application of the wood pressed on the basis of the bamboo, in the rehabilitative solutions of the architectonic patrimony constructed in wood and located in Cayo Granma and his outskirts, encountering preliminary schemata of proposal of constructive system on the basis of components elaborated starting from chessboards pressed of bamboo that retakes the beginnings, forms and the balloon's procedures frame, solution that he characterizes to many of antique solutions, necessary retrieving from Santiago of Cuba, in this context placed at the Bay. [ABSTRACT FROM AUTHOR]

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This study examined the formation and growth of secondary organic aerosols (SOA) generated when ozone was added to a 1m3 glass chamber that contained either pine shelving, oriented strand board (OSB), beech boards, or beach boards painted with an “eco” paint. The experiments were conducted at close to real-world conditions; the chamber was ventilated at ∼0.5 air changes/h; the loadings (exposed surface of building materials to chamber volume) were in the range of 1–2.5m2 m−3; and the initial O3 concentrations were between 15 and 40 ppb. Throughout each experiment particles were measured with both a condensation nuclei counter and an optical counter, while terpenes were measured before and after the ozone exposure period using sorbent tubes. The pine boards emitted primarily α-pinene and 3-carene and lesser amounts of 5 other terpenes; when O3 was introduced, the particle counts increased dramatically; the mass concentration reached ∼15μgm−3 at ∼20ppb O3, and ∼95μgm−3 at ∼40ppb O3. The OSB emitted primarily limonene and α-pinene. Although the particle counts increased when O3 was introduced, the increase was not as large as anticipated based on the terpene concentrations. The beech boards emitted negligible quantities of terpenes, and the introduction of O3 resulted in almost no increase in the particle concentration. Beech boards painted with an “eco” paint emitted large amounts of limonene and lesser amounts of carvone; upon introduction of O3 the particle counts increased sharply with the mass concentration reaching ∼20μgm−3 at ∼15ppb O3 and ∼160μgm−3 at ∼35ppb O3. These experiments demonstrate that the emission of terpenes and potential generation of SOA varies greatly among different types of wood and pressed wood materials. In the case of the pine boards and painted beech boards, the SOA concentrations generated at modest O3 concentrations approach or exceed current guideline levels for PM2.5 established by the US EPA and the World Health Organization. [Copyright &y& Elsevier]

We screened cDNA fragments that change their expression during compression wood formation by fluorescent differential display (FDD) in five adult trees (Chamaecyparis obtusa (Siebold & Zucc.) Endl.) growing naturally at an angle to the vertical, and in two saplings, one vertical, the other inclined. We conducted anatomical observations and measurements of the released strain of growth stress on the five adult trees to confirm that they formed compression wood on the lower side of the inclined trunks. Based on sequencing results from selected cDNA fragments, we conducted homology searches of the GenBank database and designed specific primers for the 67 screened fragments. Using these primers and different saplings from those used for the FDD screening, we tested the expression levels of each fragment in normal, compression and opposite wood regions of saplings by semiquantitative reverse-transcription polymerase chain reaction. Twenty-four fragments showed reproducible expression patterns, indicating that these fragments changed their expression during compression wood formation. Some fragments showed differential expression between the apical and basal regions of the lower side of the inclined stem in the region of compression wood formation. Anatomical observations indicated more intense compression wood formation in the basal region than in the apical region of the stem, demonstrating a relationship between compression wood development and gene expression. [ABSTRACT FROM AUTHOR]

A novel wood-based composite has been developed for use in structural applications. The process was designed to utilize rapidly-grown, low density, wood species. Plantation grown radiata pine is particularly well suited to this process. This is a laminated composite, where the lamina may be comprised of various materials, some of which have been treated with the viscoelastic thermal compression (VTC) process. The VTC process increases the density of wood, without causing fractures in the cell wall, thus increasing strength and stiffness of the wood material. The process may be applied to veneer, sawn wood, or strand composites. The VTC lamina is then bonded to other lamina to produce the final product. The strength and stiffness of this VTC composite exceeds any wood-based composite that is currently on the market. For example, modulus of elasticity in bending of over 20 GPa is easily obtainable. [ABSTRACT FROM AUTHOR]

Within the framework of the mechanics of heterophase systems a mathematical model for the process of pressing wood has been offered; this model takes account of the influence of its complex rheological properties and surface phenomena in thin interlayers of water on the change in a porous structure. With numerical methods, a study has been made of the influence of the sample’s humidity and temperature fields on the strength and quality of the material obtained. [ABSTRACT FROM AUTHOR]

The nanostructure of the wood cell wall and, in particular the tilt angle of the cellulose fibrils versus the longitudinal cell axis (microfibril angle, MFA), are known to play a key role in determining the mechanical properties of wood. A variation of microfibril angles during growth may therefore be regarded as a means to adapt to different loading situations. In the present study, a branch of Norway spruce ( Picea abies) was used as a model system. The change of microfibril angles with increasing age and size of the branch and therefore increasing gravitational load was systematically investigated. Small angle X-ray scattering (SAXS) was applied to obtain a map of MFA all over the branch as a function of the distance from the trunk within each annual ring. It was found that in compression wood the MFA decreased continuously from the trunk towards the tip in all annual rings. In opposite wood, however, the course of microfibril angles was found to change considerably with the age of the branch: in the outer annual rings, very small microfibril angles occurred in the middle part of the branch. The results are discussed in view of the mechanical implications of different microfibril angles. [ABSTRACT FROM AUTHOR]