Rotary-cut Veneer Research Articles

Method for determination of beech veneer behavior under compressive load using the short-span compression test

A method for the determination of mechanical properties under compressive load is presented in this study. The short-span compression test is standardized for paper-based materials and was adapted for veneer in this study. Rotary cut veneer and solid wood of European beech (Fagus sylvatica L.) was tested parallel and transversal to fiber direction. The veneer thickness was varied between 1 and 3 mm. The mechanical properties Young’s modulus, Poisson’s ratio, yield point and compressive strength were measured. The results show that the correct determination of Poisson's ratio depends on the veneer thickness as well as on the fiber direction. For veneer with a thickness of at least 3 mm, it is suitable in fiber direction, but not transversal to the fiber direction. The comparison of the mechanical properties between veneer and solid wood confirms that the lathe checks mainly influence the veneer properties transversal to the fiber direction.

Selected Properties of Plywood Bonded with Low-Density Polyethylene Film from Different Wood Species.

In this work, the effects of wood species and thickness of low-density polyethylene (LDPE) film on the properties of environmentally-friendly plywood were studied. Rotary-cut veneers from four wood species (beech, birch, hornbeam and poplar) and LDPE film of four thicknesses (50, 80, 100 and 150 µm) as an adhesive were used for making plywood samples. The findings of this study demonstrated that plywood samples using all the investigated wood species bonded with LDPE film showed satisfactory physical–mechanical properties. Poplar veneer provided the lowest values for bending strength, modulus of elasticity and thickness swelling of all the plywood samples, but the bonding strength was at the same level as birch and hornbeam veneer. Beech plywood samples had the best mechanical properties. An increase in LDPE film thickness improved the physical–mechanical properties of plastic-bonded plywood.

Effect of veneer drying process on some technological properties of polystyrene composite plywood panels

The aim of study was to determine the effect of veneer drying process on some technological properties of polystyrene composite plywood panels. For this reason, 2 mm-thick rotary cut veneers were obtained from beech (Fagus orientalis, Lipsky), Alder (Alnus glutinosa subsp. Barbata) and Scots pine (Pinus sylvestris L.) logs. The veneers obtained from three different wood species were divided into two groups to produce polystyrene composite plywood (PCP) and traditional plywood. While PCP was produced both air dried (at 20 °C) and oven dried (at 110 °C), the veneer sheets for production of traditional plywood were dried at 110 °C until reaching 7 % equilibrium moisture content. Two different types of polystyrene with high density (30 kg/m3) and low density (16 kg/m3) were used as bonding material for PCP panel production. The urea-formaldehyde adhesive was used as a bonding material for traditional plywood panels. Bonding shear strength, bending strength, modulus of elasticity and density of plywood and polystyrene composite plywood panels were investigated. It was found that the technological properties observed in the study of composite plywood panels manufactured with natural dried veneers gave similar results compared to those of composites produced with technical dried veneers.

Comparison of Birch and Beech Wood in Terms of Economic and Technological Properties for Plywood Manufacturing

The aim of this study was to investigate the use of birch wood, one of the most important wood species used in the plywood industry, especially in Europe, the Nordic countries, Poland, Belarus and Russia as an alternative to beech wood. For this purpose, comparison was made of their economic and technological properties. In five-ply plywood manufacturing, beech (Fagus orientalis Lipsky) and birch (Betula pendula) veneer sheets were used with melamine urea formaldehyde (MUF) and urea formaldehyde (UF) resins. Some mechanical properties such as shear strength, bending strength and modulus of elasticity of plywood panels were conducted according to EN 314-1 and EN 310, respectively. Mean mechanical strength obtained for birch plywood panels was quite above the limit values specified in the related standards. When taking into consideration the annual increment of beech and birch trees in 1 ha and the time they need to reach suitable diameters for the manufacturing of rotary cut veneers, it was calculated that birch trees provide 2.46 times more physical harvesting than beech trees.

Вплив пінополістиролу на процес прогрівання стружково-полімерного пакета


 Досліджено вплив пінополістиролу на процес прогрівання стружково-полімерного пакета в процесі пресування легких стружкових плит. Для фіксації температури, до якої прогрівається внутрішній шар стружково-полімерного пакета, використано мультиметр з приєднаною до нього термопарою, яку було розміщено всередині пакета. Пресування здійснювалося за питомого тиску пресування 2,4 МПа і температури плит преса 200 С. Пресували легкі стружкові плити (без пінополістиролу та з вмістом пінополістиролу 4, 7, 10%) розмірами 300×300×18 мм і щільністю 350, 450 і 550 кг/м3, личковані лущеним шпоном. Встановлено, що тривалість прогрівання стружково-полімерного пакета легких стружкових плит зменшується за збільшення в них вмісту пінополістиролу до 7%, після чого починає зростати. Додавання пінополістиролу до стружки спричиняє заповнення пустот з одночасним зростанням кількості контактів між стружкою, через яку передається тепло від периферії до центру стружково-полімерного пакета. Зростання вмісту пінополістиролу в стружково-полімерному пакеті більше 7% зумовлює сповільнення його прогрівання через те, що об’єм пінополістиролу є більшим, ніж стружки, а теплопровідність пінополістиролу є меншою порівняно з деревиною. Зі збільшенням щільності плит з 350 до 550 кг/м3 тривалість прогрівання стружково-полімерного пакета зменшується. Більша маса стружки в одиниці об’єму пакета зменшує його пористість, збільшує теплопровідність і, як наслідок, спричиняє швидше його прогрівання. Значення тривалості прогрівання середнього шару пакета легких стружкових плит до 100 oС із вмістом пінополістиролу 7% є меншим на 12-33%, ніж плит без пінополістиролу. Отримані результати дають змогу підвищити ефективність процесу пресування легких стружкових плит з вмістом пінополістиролу.

Developing the model of an automated rotary-cut veneer sorting system

The paper suggests an approach to developing the veneer sorting model based on fuzzy logic. Wide implementation and development of automated rotary-cut veneer sorting system is inhibited by the difficulties when creating analytical models. The reasonability of using fuzzy logics for veneer sorting is due to the large number of factors having significant impact, and rich expertise of engineers. The model was built and tested for two main factors: the number of healthy and deformed knots. Further studies shall be aimed at increasing the number of factors considered, collecting statistic and expert information in order to build membership functions for linguistic variables, and forming the base of rules bringing relation between the input and output variables.

Influence of thermo-vacuum treatment on bending properties of poplar rotary-cut veneer

The present paper investigates the influence of thermo-vacuum treatment at 170, 190 and 210 °C on the mechanical and physical properties of poplar wood rotary-cut veneers obtained from two different poplar clones (’I-214’ and ’Lena’). The modulus of rupture in bending was determined according to a method derived from European Standard EN-310 and previously validated by the authors, while the density was determined on the basis of EN-323. With both clones no significant decrease was recorded either in bending strength or in density with treatment temperatures up to 190 °C. On the contrary, at 210 °C a highly significant decrease in modulus of rupture (’I-214’: -18%; ’Lena’: -15%) was recorded; the density showed a similar, though lower, trend (’I-214’: -5 %; ’Lena’: -8.5 %).

Характеризация удельной поверхности древесины при эффекте памяти формы

The change of the specific wood surface at the shape memory effect is considered in this paper. The study was conducted using sorptive analyzer of specific surface and distribution of pores according to the size of Quadrasorb SI. Specific surface of samples SSA, сm2/g, was found by the low-temperature adsorption of krypton at liquid nitrogen temperature (77K) and was cal-culated by the Brunauer-Emmett-Teller (BET) method. The samples of beech, pine, oak sliced veneer and birch rotary-cut veneer were investigated.

Experimental design to determine the manufacturing parameters of a green-glued plywood panel

The objective of this research was to investigate the technical feasibility of producing plywood by green-gluing technology. 2.5 mm thick rotary cut veneers obtained from steamed maritime pine (Pinus pinaster Ait.) logs were used. Plywood was manufactured under vacuum with veneers in a wet state. Five-layer plywood panels were produced using a one-component polyurethane adhesive to evaluate the effects of two parameters, the wood moisture content and the amount of adhesive, on the mechanical properties of plywood. First, a full factorial experimental design was realised to study the bond performance. Shear tests were carried out in order to determine the bond quality and failure type. It was observed that the values of plywood panels’ shear strength depend more on the wood moisture content than on the amount of adhesive applied. A model representing the shear strength of the panels according to the manufacturing parameters was established by using statistical analyses. Another part of this study focused on microscopic observations of the bondline in order to get information about the joint morphology and the degree of adhesive penetration into the wood structure. Results suggested that definite proportions of water (moisture content between 30 and 60 %) and adhesive have to be present on wood surface when gluing to create efficient bonds. These analyses were followed by the panel’s characterisation in flexure to validate the process.

Developing and Evaluating Composites Based on Plantation Eucalyptus Rotary-cut Veneer and High-density Polyethylene Film as Novel Building Materials

To achieve value-added utilizations of plantation timbers, eucalyptus veneer/high-density polyethylene film composites were prepared, with process-factors (PF) (hot-pressing temperature, HT; hot-pressing duration, HD; hot-pressing pressure, HP; HDPE-film content, HC) and composite-properties (CP) (water-resistant bonding-strength, BS; modulus of rupture, MOR; modulus of elasticity, MOE) investigated. According to thermal analyses, 140 to 180 °C was appropriate for HT. Based on statistical analyses, HD was easier to affect CP, while MOE was easier to be affected by PF. Quantitative relationships between PF and CP were determined by the neural-network (ANN) modeling. In ANN simulation surveys, CP displayed Gaussian distributions (R2 > 0.9) when PF changed in current ranges, with positive correlations between BS and MOR (R2 ≈ 0.5). Combining ANN and the genetic-algorithm, optimal processes (HT, 160 °C; HD, 50 s/mm; HP, 1.3 MPa; HC, 6 layers) were found, and optimal results (BS, 1.30 MPa; MOR, 86.94 MPa; MOE, 8.33 GPa) were comparable to various reported poplar-plywoods. Microscopic images demonstrated that composite interfaces were formed by the mechanical interlocking. The optimal BS attained Chinese standards for water-resistant plywoods, so proposed composites can serve as water-resistant and formaldehyde-free building materials for furniture and interior design.

Preliminary study on the variation of the bending properties of poplar rotary-cut veneer

The authors studied the variability of mechanical properties and density within poplar wood veneer. Determinations (EN 310 1993) were done using a tensometer particularly suitable for test pieces of small dimensions, by means of a 100 daN load cell. The bending test method developed seems to be able to provide reliable results, that confirmed the expected strong influence of the ring portions on both density and MOR (latewood being of course heavier and stronger), a difference which seems, however, less noticeable in false heartwood.

Lathe check characteristics of fast growing sengon veneers and their effect on LVL glue-bond and bending strength

Fast growing sengon (Paraserianthes moluccana) is largely rotary-cut to produce veneer for core plywood production. In order to provide better information on veneer production and utilization, in this study the effects of wood juvenility and veneer thickness on lathe checks of rotary-cut sengon veneers were evaluated. Before veneer manufacturing, sengon logs were boiled at 50°C and 75°C for 4 and 8h, respectively. The boiled logs were peeled to produce veneer of 1, 1.5, and 2mm in thickness. Lathe checks of veneers were measured on the loosed side at every 5mm veneer length under an optical video microscope and their frequency, depth, and length were characterized. Twenty sampling points of 5mm veneer length were prepared from each segmented ring of 1cm width from pith to bark. Isocyanate resin adhesive were used to produce laminated veneer lumber (LVL) of 20mm thick, which consisted of 24-ply of 1mm veneer thick, 14-ply of 1.5mm veneer thick, and 11-ply of 2mm veneer thick, for glue bond and bending strength test. Results showed that wood juvenility and veneer thickness determined the frequency, depth and length of lathe checks for the sengon rotary-cut veneers. In general, the frequency of lathe checks of the veneer increases with increasing veneer thickness, and also increases from pith to bark. Boiling of logs before rotary-cutting could decreases the frequency of lathe check of the veneer. The results indicated that boiling of logs at 50°C for 8h and at 75°C at least 4h before peeling the logs could minimize the frequency of lathe check in manufacturing rotary cut veneer thickness of 1, 1.5, and 2mm from juvenile wood of fast growing sengon. The frequency of lathe check affects significantly the glue bond and bending strength, in which the glue bond, modulus of elasticity (MOE), and modulus of rupture (MOR) decrease as the frequency of lathe checks increases.

Effects of plasma treatment and sanding process on surface roughness of wood veneers

An ideal veneer surface is crucial for good panel properties in plywood manufacturing. The aim of this study was to compare plasma treatments and sanding (mechanical) processes with respect to the surface roughness of veneers. Rotary-cut veneers with a thickness of 2 mm from Scots pine (Pinus sylvestris) logs were used as material. After rotary peeling, veneer sheets were dried at 110 °C in a veneer dryer. Veneer sheets were divided into 4 main groups. The surfaces of the control veneer sheets were left untreated. Two different grits of sandpaper, 80 and 180, were used for sanding the surfaces of veneers. Plasma treatment was applied to the last veneer group with 3 different gases (oxygen, nitrogen, and ammonia) and 3 different plasma times (1 min, 5 min, and 15 min). The Mitutoyo Surftest SJ-301 instrument was used to determine surface roughness of samples. Average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) parameters were measured to evaluate the surface roughness of the samples based on DIN 4768. It was found that the smoothest veneer surfaces were obtained with the sanding processes. Surface roughness values (Rz) of veneer sheets sanded with 180 grit sandpaper were lower than those of veneers sanded with 80 grit sandpaper. Compared with the plasma treatment in terms of surface roughness, plasma-treated veneers had higher Rz values. It was also determined that Rz values were the lowest in the veneers treated with nitrogen plasma. Additionally, the surface roughness values of Scots pine veneers treated with ammonia plasma were a little higher than those of veneer sheets treated with oxygen plasma. The effect of plasma treatment time on surface roughness was not found to be statistically significant.

Some physical properties of plywood produced from beech, poplar and eucalyptus veneers

In this study, in three different combinations and five ply plywood boards were produced from beech (Fagus orientalis L.), eucalyptus (Eucalyptus grandis W. Hill ex Maiden) and hybrid poplar (Populus x euramericana I-214 clone) rotary cut veneers using urea-formaldehyde (UF), melamine-urea formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Physical properties e.g. air-dry density, thickness swelling and water absorption of produced plywood boards were determined. The measurements of thickness swelling and water absorption were made at the end of 2, 24, 168 and 336 h times. The effects of factors of adhesive type, combination type and time on the thickness swelling and water absorption were investigated. As a result of ANOVA test, it was determined that the effects of all three factors on the thickness swelling and water absorption were significant, statistically. According to adhesive type, the lowest thickness swelling and water absorption were determined on the plywood bonded with MUF, the highest were determined on the plywood bonded with PF. According to combination type, the lowest thickness swelling was determined on the plywood produced with eucalyptus and poplar combination. The lowest water absorption was determined on the plywood produced with beech and eucalyptus combination. Keywords: Plywood, Thickness swelling, Water absorption, Eucalyptus, Poplar, Beech

Characteristics of Sengon Rotary-Cut Veneer

Fast growing sengon is largely rotary-cut to produce veneer for plywood, com-ply and LVL. In order to provide better information on veneer production and utilization, in this study the effects of wood juvenility and veneer thickness on lathe checks of sengon rotary-cut veneer were evaluated. Before veneer manufacturing, the sengon log was boiled at 50 and 75 oC for 4 and 8 h, respectively. The boiled logs were peeled to produce veneer of 1 and 2 mm in thickness. Lathe checks of veneers were measured under an optical video microscope. The rotary-cut veneer was grouped and evaluated separately at every segmented ring of 2 cm from pith to bark. The results showed that wood juvenility and veneer thickness had an important effect on lathe checks for the rotary-cut veneer. In general, the number of lathe check of the veneer increases with increasing veneer thickness and increase from pith to bark. Boiling of logs before rotary-cutting could decrease the value of lathe check. The results indicated that boiling of logs at 50 oC for 8 h, and at 75 oC for 4 and 8 h could minimize the number of lathe checks in manufacturing of 1 and 2 mm rotary-cut veneer from juvenile wood sengon. Key words: juvenility, lathe check, Paraserianthes falcataria, rotary-cut veneer, veneer thickness

Investigation on bonding quality of beech wood (Fagus orientalis L.) veneer during high temperature drying and aging

In the present study, the effects of high drying temperature and UV light induced aging on bonding quality of plywood manufactured from untreated and treated veneer layers were investigated. Rotary cut veneers with dimensions of 500 mm×500 mm×2 mm produced from beech (Fagus orientalis Lipsky) log were selected for topochemical, chemical and mechanical analyses. The veneer sheets were oven-dried at 100°C and 180°C after the peeling process. Afterwards, the surfaces were exposed to artificial UV irradiation in an UV chamber for 24 h, 48 h and 72 h representing natural sun irradiation of 2, 4 and 6 months, respectively. Topochemical distribution of lignin and phenolic extractives of the treated and untreated veneers was investigated on a cellular level using UV microspectrophotometry (UMSP). For the chemical characterization of accessory compounds high performance liquid chromatography (HPLC) was used. Furthermore, the shear and bending strengths of plywood manufactured from the treated samples are determined in order to study the bonding quality. The UV microscopic detection shows that after high drying temperature and aging treatment, lignin condensation occurs. With increasing drying temperature and aging duration, more phenolic extractives are situated in parenchyma cells and vessel lumens which can be proved by increased absorbance at 278 nm. The HPLC analysis of the treated tissue showed distinct signals of polymerized compounds such as catechin and 2,6-dimethoxybenzoquinone which are chromophoric compounds in discolored beech wood. The mechanical properties of plywood showed that with increasing drying temperature up to 180°C does not negatively affect shear and bending strengths of samples. After exposure of the veneers to UV irradiation (especially 6 months), decreasing shear and bending strengths of plywood samples can be observed.

Physical and mechanical properties of plywood manufactured from treated red-heart beech (Fagus orientalis L.) wood veneers

Effects of drying temperature and artificial UV irradiation on the pH of veneer surfaces, water absorption, thickness swelling, as well as shear strength of plywood manufactured from untreated and treated veneer sheets were evaluated. Rotary cut veneer sheets from beech (Fagus orientalis Lipsky) log were selected. The veneer sheets were dried at either 100°C or 180°C after peeling. Then the surfaces were exposed to artificial UV irradiation in an UV chamber for 1, 2, and 3 days representing a natural sun irradiation of 2, 4, and 6 months, respectively. Tests by UV microspectrophotometry showed that after high temperature drying and UV irradiation treatment, lignin condensation occurs. Also with increasing drying temperature and UV irradiation duration phenolic extractives are mainly concentrated in parenchyma cells and vessel lumens. HPLC analysis of the treated tissue showed distinct signals of catechin and 2,6-dimethoxybenzoquinon, which are two chromophoric compounds in discolored red hearted beech wood. Increasing drying temperature up to 180°C improved water absorption, thickness swelling, and shear strength of plywood samples. Especially, when veneers were exposed to UV irradiation (6 months), increased water absorption and thickness swelling and decreased the shear strength of plywood samples were observed.

Effect of pre-pressing of veneer on the glueability and properties of veneer-based products

The study used a physical and environmentally friendly method to enhance the properties of both veneer and plywood. The effect of pre-pressing process factors (pressure, temperature and time) on the compression ratio, surface roughness, tensile strength perpendicular-to-grain of rotary cut veneer sheets of birch (Betula pubescens), and on the shear strength of plywood made from these compressed veneer sheets were studied in laboratory tests. The effect of pressing factors (such as pressure and glue spread) on the properties of plywood made from pre-pressed veneer was also studied. Three-layer plywood panels were manufactured from pre-pressed and non-pre-pressed veneers using phenol formaldehyde glue resins. Test results revealed that the greatest influence on properties of veneer is the pre-pressing temperature followed by the pre-pressing pressure and pre-pressing time. Meanwhile, the veneer’s properties such as surface roughness can be improved, and the properties of plywood were also improved when the birch veneers were pre-pressed. Linear relationship between the compression ratio and surface roughness was found. The tensile strength of veneer was not significantly influenced by the pre-pressing factors. The pre-pressing temperature has the largest effect on shear strength of plywood. The initial veneer densification allows lowering both glue spread from 150 to 90 g/m2 (a 40% reduction) and pressing pressure from 1.8 to 1.0 MPa (a 45% reduction). The shear strength obtained for the tested plywood meets EN 314-1 requirements. It is expected that the results of this preliminary study will lead to new gluing approaches, which will result in significant performance improvements of veneer-based products.

Effect of Relative Humidity on Reliability of Nondestructive Testing for Birch Laminated Veneer Lumber

Three different nondestructive testing (NDT) methods and the static bending test were conducted on the Laminated Veneer Lumber (LVL) made from birch (Betula platyphylla Suk.) rotary-cut veneers in this study. The NDT methods included the longitudinal vibration method, in-plane and out-plane flexural vibration method. The linear regression between dynamically elastic module and bending strength (MOR) and the effects of relative humidity on the reliability of NDT methods for LVL were investigated. There were four relative humidities including 40%, 50%, 60% and 70%. The results showed that the three non-destructive testing methods can be applied to test mechanical properties of birch LVL, the theory MOR result obtained by adjusted regression equation were reliable and can be applied in the actual project.

The effect of boiling time on the surface roughness of rotary-cut veneers from oriental beech (Fagus orientalis L.)

The objective of this study was to investigate effects of boiling time on surface roughness of beech (Fagus orientalis L.) veneer manufactured using the rotary cutting method. Three logs of oriental beech were subjected to softening process by boiling them in water (60–70