Innovative CLT panel production using heat treated wood

Abstract

The invention is located in the Forestry Products Industry. The invention relates to the production of CLT panels with middle layer orientation and heat treated material in CLT panel production.

Description

[0001]DESCRIPTION INNOVATIVE CLT PANEL PRODUCTION USING HEAT TREATED WOOD TECHNICAL FIELD OF THE INVENTION The invention is located in the Forestry Products Industry. The invention relates to the production of CLT (Cross Laminated Timber) panels with middle layer orientation and heat-treated material. BACKGROUND OF THE INVENTION CLT panels are one of the products of the Wood Based Board Industry in the Forest Products Industry, which is gaining increasing popularity in wood construction technology and wooden housing construction. CLT panel technology is a relatively new product commercialized in 1993. The heat treatment methods that can be called new and widely used today are ThermoWood method using steam in Finland, PlatoWood-Lignius-Lambowood method using steam and hot air in the Netherlands, Retification Process (Retiwood)-New Option Wood-Le Bois Perdure method using inert gas in France and Hot Oil Treatment (OHT)-Menz Holz method using hot oil in Germany. It has been reported in the literature that heat treatment application causes improvements in strength properties of wood such as compressive strength, hardness and stiffness. In addition, it has been observed that heat treatment application causes a decrease in the density, thickness, swelling percentage and bending strength values of the material. However, it was observed that the decrease in bending strength did not cause a decrease in the modulus of elasticity value in bending. In addition, heat treatment application causes a decrease in tensile strength. The higher density of hardwoods compared to softwoods causes the wood to work harder during moisture exchange, causing tension in the glue line. This tension causes separation from the wood or glue line after a certain strength point. This situation is eliminated by using primer chemicals on the surface of wood materials before gluing. The problem of stress formation in this glue line causes difficulties in the use of hardwood in CLT panel production. Since the wood material will absorb less water as a result of heat treatment application and will work less accordingly, the use of heat-treated wood material can be an alternative to the primer chemical normally used to prevent problems related to adhesion. Using Norway spruce (Picea abies) wood, produced CLT panels with 5 layers with successive layers making an angle of 45 degrees with the outer layers and 90 degrees with each other. As a result of the 4-point bending strength test, there is a 35% increase in the bending strength values in the experimental groups and a 37.3% decrease in the coefficient of variation value of this value compared to the control group. An increase of 15.5% was observed in the global modulus of elasticity value in the experimental groups and a decrease of 59.1% in the coefficient of variation value of this value compared to the control group. An increase of 15% was observed in the compressive strength values parallel to the panel surface. Produced 3-layer CLT panels with middle layer fiber angles of 30, 45 and 90 degrees using American poplar (Populus deltoides L.). In the specimens, it was observed that there was a 13.2% decrease in the bending strength value as the middle layer angle increased from 30 degrees to 90 degrees angle. In the modulus of elasticity, it was observed that there was a decrease of 2.4% as the middle layer angle went from 30 degrees to 45 degrees and a decrease of 13.6% as the middle layer angle went from 30 degrees to 90 degrees. As a result of the study, it was observed that the bending strength and modulus of elasticity values of the specimens increased with the decrease in the middle layer fiber angle. As a result of the literature studies, it has been observed that the angle orientation process in the middle layer causes an increase in the mechanical properties of the panels. As a result of the study, it was seen that the losses in bending strength and tensile strength due to heat treatment application can be compensated by 45- degree application. Building insulations applied to CLT structures are designed and constructed to keep moisture away from the structure. Therefore, it was deemed necessary to be careful about moisture management. In addition, air flow carries heat and water vapor and it is considered necessary to make insulations to prevent air flow. Finally, it is necessary to prevent heat conduction in building insulation. There is a need for alternative solutions that can be applied to CLT structures in moisture conduction, air conduction and heat conduction. As one of these solutions, heat treatment of wood material can be considered. As a result of the heat treatment application, the wood material has a low equilibrium moisture content, accordingly, the shrinkage-expansion of the wood decreases and this situation provides the wood to gain extra features such as an increase in the dimensional stability of the material, an increase in thermal insulation properties, an increase in biological resistance against fungi and insects, an increase in strength to outdoor weather conditions, decorative color diversity and an extension in the duration of use. There are a few studies in the literature about the angle change in the fiber direction of the middle layer and it is stated that there is a change in the resistance properties of the panels according to the wood type as a result of the modification made in these studies. There is no large-scale CLT panel production-patent study using heat-treated pine and ash woods in the literature. Wood materials are not durable against water. It is considered necessary to increase the strength values and water resistance of CLT panels. At this point, the middle layer angle change and the use of heat-treated material can be useful in solving these problems. DESCRIPTION OF THE INVENTION CLT panel materials work over time according to the environment in which they are located or swell in case of water contact and their structure deteriorates. The use of heat-treated wood material has given positive results in eliminating these and similar disadvantages. Dimensional stability of the produced panels can be increased. The use of these panels in areas such as toilets, bathrooms, kitchens, terraces, roofs and balconies in buildings where humidity problems may be experienced may allow the prevention of moisture-related problems that may be experienced in the building, the possibility of preventing the decay of the panels, and the useful life of the building can be extended. By reducing the moisture exchange of the panels, the weight change and dead load amount of the building can be minimized. Middle layer angle change provides an increase in the strength properties of the panels, allowing more load to be carried by using thinner panels. Explanation of Figures Figure 1. Arrangement of timbers in CLT panel production Figure 2.3-layer CLT panel with the middle layer produced at 90° angle Figure 3.3-layer CLT panel with the middle layer produced with a 45° angle Figure 4. Tensile shear strength test template Figure 5.4-point bending resistance test template Figure 6. CLT panel compressive strength perpendicular to the panel surface Figure 7. Compressive strength parallel to the CLT panel panel surface Reference list 10 CLT panels DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the preferred alternatives for the production of innovative CLT panels using the heat-treated wood subject matter of the invention are described only for a better understanding of the subject matter and in a non- limiting manner. Generally consisting of 3 to 7 layers, but can be produced in more layers when desired, the fiber directions of successive layers are usually 90° angles with the other layers, obtained by gluing the layers on top of each other, usually coniferous tree woods are used in the production of panels is called CLT panels. The arrangement of timbers in CLT production is shown in Figure 1. The individual thickness of the wood materials used in the layers for the production of the panel varies between 16mm and 51mm and the width varies between 40mm and 300mm. Wooden materials with short lengths before panel production can be joined with each other using structural glues and finger joint method when necessary, and their lengths can be extended in the desired amount. The obtained long wood materials are dried to 12±3% humidity and made ready for panel production. One of the most important genera of the Pinaceae family is pines. In our country, 5 species belonging to the Pinaceae family grow naturally. Some characteristics of yellow pine (Pinus sylvestris L.) are shown in Table 1. Table 1. Some physical and mechanical properties of yellow pine species Yellow pine wood is a material that can be easily machined and glued well. Yellow pine wood is mostly used in the production of construction timber and joinery timber, followed by the production of window and door joinery for interior and exterior decoration in buildings, bridge constructions, wire poles, mining poles, aircraft and large deck flooring, furniture and carving packaging crates. It is a valuable tree species with a wide range of uses such as decorative cutting veneer board production, plywood production, plywood production, turning, chemical production from wood, fence stakes, scaffolding, sleeper, particle board, plywood sector paper and cellulose wood. There are more than 65 species of ash belonging to the genus Fraxinus, a member of the Oleaceae family native to temperate regions of the northern hemisphere. Many of the ash species are excellent shade trees for parks and residential areas. In addition, it is one of the important forest trees that attracts attention thanks to its hard, highly resistant to shock impact, exhibiting a straight grained structure. In all ash taxa the wood is ring-porous species. The annual ring boundary is evident due to the diameter difference between the trichomes and the boundary parenchyma. Spring wood trichomes are usually distributed individually, grouping is very rare. White (American) ash (Fraxinus americana) is an elastic, commercially important hardwood species with high economic value. Its wood is used in the production of tool handles, furniture, flooring, crates, boats, doors and cabinets. Thanks to the toughness of its wood, it is a preferred material for making baseball bats, hammer handles, axe handles, skis and other wooden objects that require shock strength. Species. Table 2 shows some characteristics of American ash species. Table 2. Some characteristics of American Ash (Fraxinus americana) species Samsun poplar (I-77 / 51 Populus deltoides Bartr.) is a clone of Populus deltoides Bartr. ssp. angulata (American black poplar), a species belonging to the Aigeiros section, produced by intraspecific fertilisation. The I-77 / 51 clone of eastern poplar is a clone that was selected in Italy but was unsuccessful. However, successful results were obtained in our country, especially in the Central Black Sea Region. This species has shown better development in our country compared to I-214 hybrid poplar and has become more widespread. As a result of the studies, it was deemed appropriate to register the name of the clone as "SAMSUN". It is also known commercially as Samsun poplar or 77 / 51 poplar in the domestic market. Polyurethane glue is produced by the combination of double-bonded alcohol and suitable isocyanate structured products. The cohesion and adhesion forces of the glue are very strong. It is resistant to microorganisms, acids, oils and boiling water and its structure does not deteriorate. The reaction time required for hardening under room conditions (20 ºC) is around 60 minutes. When the hardening reaction is completed, the glue expands approximately twenty times its applied volume and disadvantages such as shrinkage in the glue layer are eliminated. Increases in the gluing temperature cause shortening of the glue curing time. However, application at temperatures above 60ºC or pressing releases gases harmful to human health and this is not recommended. The heat-treated yellow pine (Pinus sylvestris L.) and American ash (Fraxinus americana L.) timbers and the non-heat-treated yellow pine and American ash timbers used in the invention are Samsun poplar (I-77 / 51 Populus deltoides Bartr.) without heat treatment. The materials were randomly selected in accordance with the fabricated production and no attention was paid to the annual ring condition. In the structure of the heat-treated and non-heat-treated yellow pine wood materials, the presence of mostly sap and heartwood was observed. Ash wood materials, on the other hand, consisted of some heartwood, some sapwood, and some heartwood and sapwood in a mixture. In poplar materials, there was no distinguishable difference between heartwood and sapwood and there was no possibility to distinguish them. Polyurethane (PU) glue is used in the production of CLT panels. Glue application to the board draft was made on one surface of consecutive layers with 200gr / m2. In the formation of the layers, single layer solid panels were produced by gluing the timbers side by side. Then, these panels were stacked on top of each other and the glue was applied to the panel surfaces with the help of a roller in the required amounts and the board draft was made ready for pressing. The properties of the glue used are shown in Table 3. Table 3. Properties of polyurethane glue used in production Product Manufacturer Mikrokim Chemistry Component Count One Component, Moisture curing Binding Substance Polyurethane resin Density 1,10gr / cm3Solid Matter Percentage 97% Application Time (at 23 °C) 5 to 7 hours Solidification Start Above 0°C, 1 Hour Heat resistance 25°C / +125°C Curing time (20 °C) 5-7 hours Press Pressure 7kg / cm2Environmental adaptation No known negative effects Health compatibility No known harmful effects The supplied wooden materials were acclimatized. With the help of the air conditioning process, the humidity of the materials was stabilized. With the help of an automatic profile cutting machine, the knots, the appearance of the material, the thin, crusted or narrow parts of the material were cleaned and the materials were purified from defects. As a result of the defect removal process, short pieces ranging from 15cm to 75cm in length were formed and these short pieces were extended by joining end to end using the finger thread joining method and polyurethane (PU) glue according to the dimensions of the press to be used in plate production. After this stage, the surfaces of the long boards produced were cleaned with the help of 4 edge planning machine and the materials were made to be glued together. After these processes, the thickness of the boards was measured as 21 mm, width 85 mm and length 400 cm. The planed materials were glued from the side edges, pressed side by side in the solid panel press under a pressure of approximately 0,7N / mm2 until the glue line hardens (minimum 8 hours is stated on the glue package) and glued to each other and each layer of the 3-layer CLT panels to be produced was prepared separately. These single layer panels were glued on their wide surfaces this time, the layers were placed on each other and 3-layer CLT panel drafts were prepared. The drafts were pressed in the solid panel press under a pressure of approximately 0,7N / mm2 until the glue line hardened and CLT panel production was carried out. In the board production, 3-layer boards were produced separately as yellow pine- poplar-yellow pine, ash-poplar-ash in the layer sequences, using heat-treated and non-heat-treated yellow pine and ash woods in the outer layers of the boards. In all groups, woods obtained from Samsun poplar with low economic value and without heat treatment were used in the middle layer. In the production of CLT panels, the fiber direction of the wood to be used in successive layers is such that the fiber direction is at an angle of 90° with that of the other layers. In the present invention, the middle layer, i.e. the fiber direction of the second layer, is at an angle of 45° with the fiber direction of the first and third layers. The layer orientations of the produced panels are given in Figure 2 and Figure 3. Table 4 shows the experimental design of the layer arrangements. Table 4. Experimental design of working group and layer orientation N Heat Panel Layer Middle Layer Sample Code umber of Layers Treatment Arrangement (Bottom- Lamination middle- After pressing, test samples were prepared from CLT panels according to the dimensions specified in TS EN 317 ( thickness swelling), TS EN 322 (moisture content in %), TS EN 323 (density), ASTM E96 (water vapor transmission rate), ASTM C518 (thermal conductivity), TS EN 408-A1 (3-4 point bending strength and compressive strength), TS 3969 EN 314-1 (adhesion quality) standards. Yellow pine and ash woods were subjected to heat treatment. Heat treatment was applied under Thermo S conditions, and the second stage of heat treatment was carried out in accordance with the parameters of 190ºC temperature and 3.5 hours duration. The heat-treated and non-heat-treated wood materials were kept in an acclimatization chamber with a temperature of 20±2°C and a relative humidity of 65±5% until they reached constant weight and were acclimatized and made ready for use in the formation of board drafts. DETERMINATION OF AIR-DRY DENSITY AND OVEN DRY DENSITY Test specimens with dimensions of 50x50x54 mm (width x length x thickness) were prepared according to the principles in TS EN 323 to determine the air dry and oven dry density of the CLT panels produced. The samples were firstly conditioned in an air conditioning cabinet at 20±2°C and 65±5% relative humidity, then their width, length and height were measured and weighed. Air dry density values were calculated using these data. The samples were then dried in an oven at 103±2°C until they reached constant weight, cooled in a desiccator, then their width, length and height were measured and weighed. Using these data, the complete dry density values of the samples were calculated. In addition, the samples with air dry density measurements were used in thickness swelling and water absorption experiments. Air dry densities were calculated according to Equation 1 and oven dry densities were calculated according to Equation 2. where; D12: Air dry density (gr / cm3), m12: Air-dry weight of the test piece (gr), V12: Volume of the test piece in air dry state (cm3). D0= (2) where; D0: Oven dry density (gr / cm3), m0: Weight of the test piece in oven dry state (gr), V0: The volume of the test piece when oven dry state (cm3). DETERMINATION OF EQUILIBRIUM MOISTURE CONTENT Equilibrium moisture content (EMC) of the produced CLT panels were determined using samples with dimensions of 50x50x54mm (width x length x thickness) according to TS EN 322. The weights of the samples, which were kept in air conditioning at 20±2°C and 65±5% humidity until they reached constant weight and became air dry, were weighed on a scale with a precision of ±0.01gr, and then dried in an oven at 103±2°C until they reached constant weight and their oven dry weights were determined and the equilibrium moisture content of the samples in air dry state were calculated by using Equation 3. where; mr: Air dry weight of the test piece (gr), m0: Weight of the test piece in oven dry state (gr). THICKNESS SWELLING AND WATER ABSORPTION Thickness swelling (TS) and water absorption (WA) percentages for CLT panels were determined separately using 50x50x54mm (width x length x thickness) samples according to the principles in TS EN 317. In determining the swelling and water absorption percentages of CLT panels, the test specimens were kept in water with a pH value of 7±1 and a temperature of 20±3 °C for 2, 24 and 336 hours. At the end of these periods, the specimens were removed from the water and their weights and dimensions were determined. Percentages of swelling and water absorption were calculated according to Equation 4 and Equation 5. where: WA: Water absorption (%), a1: Weight of the test piece before immersion in water (g), a2: The weight of the test piece after immersion in water (gr). where: TS: Amount of swelling to thickness (%), K1: Thickness of the test piece before immersion in water (mm), K2: The thickness of the test piece after immersion in water (mm). WATER VAPOUR TRANSMISSION RATES IN BOARDS The water vapour transmission test was carried out on 30 round specimens with a diameter of 100 mm according to the principles in ASTM E96 using the cup method. This method is applied according to the principle of movement of water vapour from the high density to the low density. In the experiments, pure water was placed in plastic containers, the sample was placed on them in an airtight manner, the edges of the sample were also made airtight, 2 weeks were waited for the rate of weight change to reach equilibrium, and then the weight decrease was measured at 24 hour intervals and the water vapour transmission rate (WVTR) was calculated according to Equation 6 and the water vapour permeability was calculated according to Equation 7. where; WVTR = Water vapour transmission rate (kg / (m2s)), WVP = Water vapour permeability (kg / (m2sPa)), ^^m = Weight difference between different time weighings (kg), t= Time elapsed between sample different time weighings (sec), A= Area of contact of evaporating water on the sample (m2), h= Sample thickness (m) S= Water vapour pressure at 100% relative humidity (2489 Pa at 21ºC), R1= Relative humidity of pure water in the container (100%), R2= Outdoor relative humidity value (20% in the study). THERMAL CONDUCTIVITY OF BOARDS The thermal conductivity properties of the specimens obtained from CLT panels were determined using 300x300x54mm (width x length x thickness) specimens according to the principles in ASTM C518. At the beginning of the experiment, the thickness of the sample was entered into the test device and the device calculated the thermal conductivity value by using this thickness. The experiments were carried out in accordance with the average temperature 23ºC conditions. Equation 8 and Equation 9 were used to calculate the thermal conductivity (C) and thermal resistance (R) values. where; C: Thermal conductivity (W / (mK)), S: Heat flow sensor calibration factor, E: Heat flow sensor output voltage (V), ^^t: Temperature measurement difference between 2 outer surfaces of the sample (°C), R: Thermal resistance of the material ((mK) / W). GLUE ADHESION QUALITY Glue adhesion quality test was prepared according to the principles specified in TS 3969 EN 314-1 from wood materials sawn in the dimensions of 10x20x150mm (thickness x width x length) by gluing 2 layers together with a sample thickness of 5mm. The specimens were glued to each other with polyurethane (PU) glue and test specimens were obtained. The specimens were tested by applying tensile force to the specimens after the tester was set to tensile at a speed of 2 mm / min. The maximum force at break (Fmax) was determined and the adhesion strength (σy) was calculated according to Equation 10. Glue adhesion quality test template is shown in Figure 4. where; Fmax: Maximum detected force value (N), A: Adhesion surface area (mm2). FOUR POINT BENDING TEST AND MODULUS OF ELASTICITY Four-point bending test was applied to specimens with dimensions of 25 54x305x1260mm (thickness x width x length) according to the principles in TS EN 408-A1 (2012). It is stated in TS EN 408-A1 (2012) that the spacing between the bearings should be between 18±3 times the specimen thickness (h). In the study, the bearing spacing was set as 20 times the thickness. In addition, the ANSI / APA PRG 320 (2019) standard states that specimen widths should be a minimum of 305 mm. During the test, the load application was perpendicular to the panel surface and the test speed was adjusted so that the specimen would break within 300±120 seconds for CLT panels. The bending strength values (σe) (MOR) of the specimens were calculated according to Equation 11, the modulus of elasticity (MOE) values were calculated according to Equation 12 and the bending stiffness (EImg) was calculated according to Equation 13.Bending Strength (MOR): 3^^. ^^^^^^^^⁄ ^^. ℎ2 (11) Modulus of Elasticity Global (MOE):^^2−16.^^ 2.^^.ℎ3(2^^^^2−^^1− 5.^^.^^.ℎ) (12) Bending Stiffness Global (Elmg): where; EImg=K= Flexural rigidity (N.mm2), Fmax= Maximum amount of force observed at the moment of fracture (N), a= Distance between bearings and loading arm (7h), (mm), b= Sample width (mm), h= Sample thickness (mm), L= Clearance between bottom supports (mm), G= Shear modulus (N / mm2), F2-F1= Corresponding to 10% and 40% of the maximum force in the Force- Deformation curve difference between the increase in force (N), w2 - w1= F2 - difference between the deformation increase corresponding to F1 (mm). COMPRESSIVE STRENGTH TEST For the test of CLT panels, compressive strength specimens parallel to the fibers with dimensions of 54x100x324mm (thickness x width x length) and compressive strength specimens perpendicular to the fibers with dimensions of 54x100x100mm (thickness x width x depth) were prepared according to TS EN 408-A1 (2012) and kept in the air conditioning cabinet for 1 month and air dried. The dimensions of the specimens were measured with a 0.01mm caliper and the loading speed of the test device was adjusted so that the fracture time for the panels was 300±120 seconds. The force at fracture (Fmax) was measured and the compressive resistance values (σB) were calculated according to Equation 14. where; Fmax= Maximum force at the moment of fracture (N), a = Width perpendicular and parallel to the panel surfaces (mm), b = Depth when pressed perpendicular to the panel surfaces, thickness when pressed parallel (mm). FINDINGS As a result of the air-dry density and oven dry density determination experiments, the oven dry densities of CLT panels were observed from less to more in the following order: yellow pine groups with heat treatment, yellow pine groups without heat treatment, ash groups with heat treatment and ash groups without heat treatment. It was observed that there was a 6.1% decrease in density between the yellow pine group without heat treatment and the yellow pine group with heat treatment, and a 14.48% decrease between the ash group without heat treatment and the ash group with heat treatment. In the 90 degree and 45-degree groups, since it was thought that the middle layer angle change would not have an effect on the density, no separate calculation was made between the groups. Full dry and air-dry densities of the CLT panels produced are shown in Table 5 and Table 6. Table 5. Oven dry densities of CLT panels Panel Type Number of Samples S 90-45 TS 90-45 K 90-45 D 90-45 TD 90-45 Mean (g / cm3) 10 0,426 0,4 0,38 0,587 0,502 Coefficient of Variation (%) 4,93 3 4,74 2,56 7,57 Table 6. Air dry densities of CLT panels Panel Type Number of Samples S 90-45 TS 90-45 K 90-45 D 90-45 TD 90-45 Mean (g / cm3) 10 0,459 0,411 0,408 0,627 0,522 Coefficient of Variation (%) 4,36 2,68 4,66 2,07 7,28 When the air-dry equilibrium moisture percentages were analyzed, it was observed that yellow pine panels without heat treatment had the highest moisture content, followed by ash panels without heat treatment, yellow pine panels with heat treatment and ash panels with heat treatment. Air dry moisture percentages of the produced panels are shown in Table 7. Table 7. Air dry humidity percentages of CLT panels Panel Type Number of Samples S 90-45 TS 90-45 K 90-45 D 90-45 TD 90-45 Mean 10 Thickness and weight increases of CLT panels after soaking in water were analyzed. After 2 hours of soaking in water, the maximum thickness increase was observed in the untreated yellow pine 45 and 90 groups, and the maximum weight increase was observed in the untreated yellow pine 90 group. After 24 hours of soaking in water, the highest thickness increase was observed in the yellow pine 45 group without heat treatment and the highest weight increase was observed in the yellow pine 90 group without heat treatment. After 2 weeks of standing in water, the maximum thickness increase occurred in the ash 90 and 45 groups without heat treatment, and the maximum weight increase occurred in the yellow pine 90 group without heat treatment. The average weight and thickness increase percentages of the CLT panels produced after 2 hours, 24 hours and 2 weeks of soaking are shown in Table 8. Table 8. Average weight and thickness increases and coefficient of variation (%) values of CLT panels after soaking in water for 2 hours, 24 hours and 2 weeks Sample Number Average Percentage Increase Average Weight Increase Group of in Thickness (%) Percentages (%) Samples 2 Hours 24 Hours 2 weeks 2 Hours 24 Hours 2 weeks S 90 10 1,21 3,08 5,13 11,81 29,29 73,83 TS 45 10 0,46 1,82 3,31 9,34 23,8 70,62 D 45 10 0,66 3,22 7,04 6,67 21,06 68,69 (34,75) (10,68) (13,54) (3,71) (5,18) (3,75) TD 90 10 0,382 1,66 3,39 5,8 15,55 50,99 (4,66) (9,85) (6,64) (9,97) (5,38) (7,56) TD 45 10 0,38 1,5 3,2 9,81 21,17 59,06 (13,3) (7,36) (5,43) (40,28) (18,19) (8,45) When the water vapor transmission rates of the panels in the environment containing 20% relative humidity were examined, it was observed that the highest transmission was observed in the yellow pine groups without heat treatment. The least transmission was observed in the heat-treated yellow pine groups. Close values were found in ash groups with and without heat treatment. The water vapor transmission rates of the CLT panels produced in an environment containing 20% relative humidity are shown in Table 9. Table 9. Water vapor transmission rates in panels Sample Number of Mean Value (kg / (m2.s)) Coefficient of K 90 5 2,801x10-714,89 K 45 5 2,182x10-716,77 D 90 5 3,539x10-72,5 D 45 5 2,949x10-711,77 TD 90 5 2,986x10-712,64 TD 45 5 3,155x10-79,62 The highest thermal conductivity values of the produced CLT panels at 23ºC were observed in ash 90 group panels without heat treatment and the lowest value was observed in heat treated yellow pine 90 group panels. In terms of thermal conductivity, a 12,86% decrease was observed between yellow pine 90 group without heat treatment and yellow pine 90 group with heat treatment, a 20,57% decrease between yellow pine 45 group without heat treatment and yellow pine 45 group with heat treatment, a 14,07% decrease between ash 90 group without heat treatment and ash 90 group with heat treatment, and an 8,52% decrease between ash 45 group without heat treatment and ash 45 group with heat treatment. Heat treatment application caused a decrease in thermal conductivity, while the middle layer angle change caused an increase in conductivity in yellow pine without heat treatment and a decrease in other groups. The thermal conductivity values of the CLT panels produced are shown in Table 10. Table 10. Thermal conductivity values of CLT panels Sample Number of Mean Value Coefficient of Group Samples (W / (mK)) Variation (%) S 90 3 0,1185 1,27 S 45 3 0,126 0,95 TS 90 3 0,105 2,86 TS 45 3 0,1045 0,48 K 90 3 0,1085 1,38 K 45 3 0,1065 1,41 D 90 3 0,15 2,67 D 45 3 0,14 0,71 TD 90 3 0,1315 1,14 TD 45 3 0,129 3,88 When the glue adhesion strength data of the wood materials used in production were analyzed, a 44.43% decrease was observed between the yellow pine-poplar group and the thermo yellow pine-poplar group in terms of glue adhesion strength, there was a 21.75% increase between ash-poplar and thermo ash-poplar, a 53.98% decrease between yellow pine-yellow pine and thermo yellow pine-thermo yellow pine group, and an 18.57% decrease between ash-ash and thermo ash-thermo ash group. When the data were analyzed, it was seen that the decrease in adhesion strength due to heat treatment application decreased from 53.98% to 44.43% when unheat- treated and heat-treated yellow pine are glued among themselves, and it was seen that the use of poplar in the middle layer can provide a positive improvement in the rate of decrease in adhesion strength in heat treated materials. Similarly, as a result of the bonding of ash materials without heat treatment and with heat treatment, it was observed that there was an increase in glue adhesion strength instead of a decrease as a result of heat treatment application and the use of poplar in the middle layer. It was observed that there was a 5.55% decrease between yellow pine-yellow pine and yellow pine-poplar group, a 14.06% increase between thermo yellow pine- thermo yellow pine and thermo yellow pine-poplar group, a 15.61% decrease between ash-ash group and ash-poplar group, and a 26.17% increase between thermo ash-thermo ash and thermo ash-poplar. As a result, it was observed that a better adhesion strength was formed between the heat-treated materials and poplar, while the opposite situation was observed in the non-heat-treated materials and it was determined that the adhesion strengths formed between non-heat-treated woods with poplar decreased. Glue adhesion strength (tensile-shear strength) test data are shown in Table 11. Table 11. Tensile-shear strength values of the specimens Join Type Number of Mean Value Coefficient of pine-Thermo 10 2,49 16,87 yellow pine 4 The highest 4-point bending strength and modulus of elasticity values of the panels were observed in ash 45 group panels without heat treatment. When 90 degree groups and 45 degree groups were compared, bending strength and modulus of elasticity decreased by 9.04% and 17.5%, respectively, in the yellow pine 45 group without heat treatment, while bending strength and modulus of elasticity decreased by 3.52% and 1%, respectively, in the yellow pine 45 group with heat treatment, 4% increase was observed, bending strength and modulus of elasticity increased by 119.11% and 52.81% respectively in the ash 45 group without heat treatment, and bending strength and modulus of elasticity increased by 28.83% and 11.86% respectively in the ash 45 group with heat treatment. The values obtained as a result of the study were compared with the values in ANSI APA PRG 320 (2019), CLT panel production standard. As a result of the comparison, it was seen that the yellow pine 90 and 45 groups without heat treatment met the E3 class in terms of flexural strength and modulus of elasticity. Although the heat-treated yellow pine 90 and 45 groups met the E3 class in terms of flexural strength, their modulus of elasticity could not meet any class. The ash 90 group without heat treatment met the E3 class in terms of flexural strength and modulus of elasticity, and the ash 45 group without heat treatment met the E1 class. Although the ash 90 group with heat treatment met the E3 class in terms of flexural strength, it could not meet any class in terms of modulus of elasticity. The heat- treated ash 45 group met the values of class E3. 4-point bending strength, modulus of elasticity and bending stiffness values are shown in Table 12 and CLT panel production classes of ANSI APA PRG 320 standard are shown in Table 13. Table 12.4-point bending strength (MOR), modulus of elasticity (MOE) and bending stiffness (EImg) values Mean Coefficient Mean Coefficie le Num nt Mean Coefficient Samp ber up o Value of Value of Value of Gro f Samples (MOR) Variation (MOE) Variation (EImg) Variation (N / mm2) (%) (N / mm2) (%) (N.mm2) (%) S 90 3 28,5 3,83 10194,34 7,25 4,83x10108,88 S 45 3 25,92 1,58 8410,53 5,07 3,99x10106,21 TS 90 3 17,89 5,6 7564,03 5,8 3,50x10104,7 TS 45 3 18,52 5,4 7669,92 7,19 3,64x10108,8 K 90 3 28,56 8,35 6229,46 4,04 2,95x10104,95 K 45 3 27,13 14,36 6447,85 4,44 3,06x10105,44 D 90 3 21,76 10,16 8460,81 6,1 4,01x10107,47 D 45 3 47,69 4,23 12932,46 3,88 6,13x10104,75 TD 90 3 24,73 5,98 7894,78 7,28 3,74x10108,91 TD 45 3 31,86 22,91 8831,24 5,32 4,19x10106,51 Table 13. ANSI APA PRG 320 standard CLT panel production classes CLT Panel 4 Point Bending 4 Point Modulus of Compressive Grade Strength (N / mm2) Elasticity (N / mm2) Strength Parallel to Fibers (N / mm2) E1 28,2 11700 19,3 E2 23,9 10300 18,1 E3 17,4 8300 15,1 E5 23,9 10300 18,1 V1 (N) 10 11000 14 V2 11,8 9500 11,5 V5 11 11000 14,8 The highest compressive strength value parallel to the fibers in CLT panels was observed in ash 90 group specimens without heat treatment. The highest compressive strength value perpendicular to the fibers was determined in ash 90- 45 group specimens without heat treatment. When the 90-degree groups and 45-degree groups were compared with each other in terms of compressive strengths parallel to the fibers, it was observed that the compressive strengths were 17.14%, 11.56% and 3.22% higher in the untreated yellow pine 45, heat treated yellow pine 45 and heat-treated ash 45 groups, respectively, compared to the untreated yellow pine 90, heat treated yellow pine 90 and heat-treated ash 90 groups. The compressive strength values in the ash 45 group without heat treatment were found to be 2.10% lower than the ash 90 group without heat treatment. Compressive strength values perpendicular to the fibers were close to each other. When the data obtained from the experiments were compared with the values in ANSI APA PRG 320 (2019), CLT panel production standard, it was seen that the compressive strength values of all groups parallel to the fibers met the E1 class (19.3N / mm2). Figures 6 and 7 show the compressive strength pattern of the CLT panels perpendicular and parallel to the fibers, and Table 14 shows the compressive strength values of the CLT panels perpendicular and parallel to the fibers. Table 14. Compressive strength values of CLT panels parallel and perpendicular to the fibers Compressive Strengths Parallel to the Panel Surface and Fiber Direction of the Outer Layer Sample Group Number of Mean Value (N / mm2 Coefficient of Samples ) Variation (%) S 90 3 22,97 4,9 S 45 3 26,9 2,37 TS 90 3 28,12 9,28 TS 45 3 31,37 6,64 K 90 3 30,79 5,4 K 45 3 28,25 4,26 D 90 3 40,94 2,37 D 45 3 40,08 2 TD 90 3 36,89 8,69 TD 45 3 38,08 10,49 Compressive Strengths Perpendicular to the Panel Surface S 90-45 3 5,28 6,97 TS 90-45 3 5,23 10,32 K 90-45 3 5,35 10,67 D 90-45 3 6,29 9,98 TD 90-45 3 4,88 9,53 Heat treatment application caused an increase in the compressive strength values of the panels parallel to the surface, 45-degree application caused an increase in the pine group panels, a slight decrease in the ash group panels without heat treatment, and an increase in the ash panels with heat treatment.

Claims

CLAIMS 1. The invention relates to the production of innovative CLT panels using heat- treated wood, characterised in that; • it is desirable to take coniferous wood, • acclimatisation of the wood to stabilise the moisture content of the wood, • the elimination of the material from defects cleaning the knot, urous appearance, thin, crusted or narrow parts of the material in the structure of the materials, • after elimination, the timbers are first joined end to end to create a layer, • the surfaces of the obtained long boards are cleaned with 4 edge planing machine and the materials are made ready to be glued together, • the planed materials should be glued to each other at the side edges, • each layer of the 3-layered CLT panel, which will be produced as a result of pressing the long boards side by side until the glue line hardens under a pressure of approximately 0.7N / mm2 in the massive panel press, is prepared separately, • the prepared single-layer panels are glued on the wide surface and the layers are placed on each other to produce 3-layer CLT panel drafts, • the final draft is pressed in the massive panel press under a pressure of approximately 0.7N / mm2 until the glue hardens and the CLT panel is produced, includes process steps.

2. The invention according to claim 1, characterised in that; polyurethane (PU) glue is used for bonding in the production of CLT panels, and is preferably 200gr / m2 on the draft panel and used on successive layer surfaces.

3. The invention according to claim 1, characterised in that; the wood species used in the outer layers of the boards are yellow pine and ash wood with and without heat treatment, and the wood species used in the layers are yellow pine- poplar- yellow pine, ash-poplar- ash, and 3 layer boards are produced one by one.

4. The invention according to claim 1, characterised in that; in the middle layer of all board groups, wood obtained from Samsun poplar (I-77 / 51 Populus deltoides Bartr.) of low economic value and without heat treatment is used.

5. The invention according to claim 1, characterised in that; the fibre direction of the wood to be used in successive layers in the production of CLT panels is at an angle of 90° with that of the other layers.

6. The invention according to claim 1, characterised in that; the fibre direction of the middle layer, that is the second layer, can be at an angle of 45° with the fibre direction of the first and third layers.

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