Bekir Cihad Bal

The Effects of Heat Treatment on Some Mechanical Properties of Juvenile Wood and Mature Wood of Eucalyptus grandis

Heat treatment is a well-known method for modifying wood that is applied in different ways, and treatment schedules change from tree to tree. This treatment improves the physical properties of wood but, in general, it reduces the mechanical properties of wood. The effects of heat treatment on the mechanical properties of juvenile and mature wood of the same tree species have not been well-defined. Therefore, we focused our study on the differences in the mechanical properties of juvenile wood and mature wood of Eucalyptus grandis after both were subjected to heat treatment. Wood samples were treated at temperatures of 120, 150, and 180°C for 4, 6, and 8 h. The test results showed that decreases in the mechanical properties of juvenile wood (e.g., modulus of elasticity (MOE), modulus of rupture (MOR), compression strength (CS), and impact bending (IB)) were greater than the decreases that occurred in mature wood that was heat treated at the same conditions.

THE EFFECTS OF WOOD SPECIES, LOAD DIRECTION, AND ADHESIVES ON BENDING PROPERTIES OF LAMINATED VENEER LUMBER

In this study, the bending strength and stiffness of laminated veneer lumber (LVL) produced from beech (Fagus orientalis L.), poplar (Populus x euramericana I-214), and eucalyptus (Eucalyptus grandis W. Hill ex Maiden) wood using urea formaldehyde (UF), melamine urea formaldehyde (MUF), and phenol formaldehyde (PF) adhesives were determined. The tests were conducted in the flatwise and edgewise directions. The modulus of rupture (MOR), modulus of elasticity (MOE), specific modulus of rupture (SMOR), and specific modulus of elasticity (SMOE) were calculated. Variance analysis of the bending properties indicated that the effects of the species of tree, the direction of the load, and the type of adhesive were statistically significant. However, according to variance analysis of the SMOR, the effects of the type of adhesive were not significant. The results showed that the type of adhesive did not influence the bending properties of laminated veneer lumber. It can be stated that the differences among groups were due to differences in their densities. The direction of the load and the species of the tree had significant effects on the bending properties.

Physical properties of beech wood thermally modified in hot oil and in hot air at various temperatures

In this study, beech wood was treated in hot oil and in hot air to determine the differences in the effects of the two processes on the physical properties of the wood. Heat treatment was conducted at temperatures of 160, 190, and 220 °C for 2 h at atmospheric pressure. After the heat treatment, various properties of the wood, including mass increase in hot oil treatment (wt% gain), mass loss in hot air treatment (wt% loss), oven-dried density, swelling, equilibrium moisture content, fiber saturation point, and moisture content were determined. Regression analyses were conducted to assess the differences in mass change and volumetric swelling, and the findings were analyzed statistically. The results showed that heat treatment in hot oil influenced the physical properties of beech wood more than treatment in hot air. However, the extensive uptake of oil by the wood samples, resulting in mass increases, was a negative issue associated with the hot oil treatment.

Some technological properties of laminated veneer lumber produced with fast-growing Poplar and Eucalyptus

Fast-growing tree species are important due to their short growth time before they are harvested. Both the Poplar and Eucalyptus species are fast-growing trees. These two species have been cultivated in many parts of the world, and they are used in several ways, including in the pulp and paper industry, as wood-based panels, and as structural composite lumber. In this study, laminated veneer lumbers were produced using different combinations of Poplar (Populus x euramericana I-214) and Eucalyptus (Eucalyptus grandis) veneers. Some physical and mechanical properties, including density, thickness swelling, water absorption, modulus of elasticity, modulus of rupture, impact bending, and bonding performance were investigated. According to the test data that were obtained, the mechanical properties of laminated veneer lumbers produced with Eucalyptus were greater than those of laminated veneer lumbers produced with Poplar. When the two were combined and Eucalyptus was used as the top and bottom plies, the mechanical properties also were better than those of Poplar laminated veneer lumbers. As a result, it can be said that both Poplar and Eucalyptus veneers can be used to produce laminated veneer lumbers, and Poplar laminated veneer lumbers can be reinforced with Eucalyptus veneers.

Kavak odununun kimyasal özellikleri üzerine termal ve basınçlı termal modifikasyon işlemlerinin etkisi

Bu calismada, hizli buyuyen ve dogal dayanikliligi az fakat onemli turlerimizden biri olan kavak odunun ( Populus usbekistanica ) cevreye dost termal islemlerle omrunun uzatilmasi planlandi. Bu amacla, yapilan testlerle hazirlanan kavak odunu numuneleri termal ve basincli termal modifikasyona maruz birakildi. Termal ve basincli termal modifikasyonun kavak odununun kimyasal ozellikleri uzerine etkisi arastirildi. Arastirma sonuclari, 160 o C’nin uzerindeki sicakliklarda odunda hemiseluloz iceriginin bozunmasindan dolayi, holoseluloz (Seluloz+hemiseluloz) miktarinin azaldigini (% 10.8) gosterdi. Ayni zamanda, basincli termal modifikasyon islemine maruz kalmis kavak orneklerinin holoseluloz iceriginin de % 2.2 oraninda azaldigi belirlendi. Ekstraktif maddelerin dikkate alinmamasindan dolayi, sicaklik artislarinin lignin miktarini da arttirdigi goruldu. Termal ve basincli termal modifikasyonu islemlerinin bir sonucu olarak, 160 o C’nin uzerinde uygulanan sicaklik derecelerinde kimyasal iceriklerde bir degredasyon olusmasina karsin, 160 o C ve altindaki sicakliklarda kavak odunu numunelerinin kimyasal ozellikleri uzerinde onemli derecede bir bozunmanin meydana gelmedigi gozlendi. Sonuc olarak, termal islem uygulama surelerinin artmasi ile, test numunelerinin holoseluloz iceriklerinde onemli bir azalma oldugu goruldu.

SCREW AND NAIL HOLDING PROPERTIES OF PLYWOOD PANELS REINFORCED WITH GLASS FIBER FABRIC

: In this study, plywood and reinforced plywood with glass fiber fabric were produced with rotary peeled poplar veneers using phenol formaldehyde adhesive. Screw and nail holding tests were conducted to obtain the characteristics of the plywood and reinforced plywood boards. One control group and three different test groups were used. The effects of glass fiber fabric on the screw direct withdrawal, screw-head pull-through, and lateral nail resistance were determined. The results of the tests indicated that the reinforced plywood’s resistances to direct withdrawal of the screw, screw-head pull-through, and lateral nail resistance were significantly higher than those of the unreinforced plywood. In addition, reinforcement of the plywood boards provided longer displacement at maximum load.