The objective of this study was to evaluate the effects of selected parameters, such as type of loading (compression and tension), the wooden dowel species, and the adhesives type on the joint stiffness. Beech, oak, and Scots pine woods were used as wooden dowel material, and polyvinylacetate (PVAc) and polyurethane (PUR) adhesives were used as adhesive agents. Elastic stiffness on diagonal tension and compression tests were applied on 120 pieces of test samples prepared. The results showed that there was found out that the highest average elastic stiffness value of 656 Nm/rad was achieved in the oak dowel joints bonded with PVAc adhesive under compression loading. The lowest average value of 293 Nm/rad was found in the Scots pine dowel joints subjected to compression stress using PUR adhesive. On average, the elastic stiffness of the oak dowel joints bonded with PVAc adhesive was 17% higher than the elastic stiffness of the Scots pine dowel joints bonded with PUR adhesive. The influence of the wooden dowel species and the adhesive type were found statistically significant

Effects of fire retardants on mechanical properties and water resistance of Pinus massoniana particleboard

Pinus massoniana Lamb. wood particleboards processed by inorganic and organic fire retardants of two densities were prepared by isocyanate and MUF resin. Variations of internal bonding strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE) and thickness swelling rate (TS) of particleboard were observed. Results demonstrated decreasing of IB from 0.81 MPa to 0.42 MPa and 0.36 MPa, MOR from 17.3 MPa to 12.5 MPa and 12.3 MPa, MOE from 1840 MPa to 1328 MPa and 1117 MPa, and increasing of TS from 5.2% to 15.1% and 11.2%, respectively, for the treated MUF particleboards of density 0.65 g.cm-3. Similarly, decreasing of IB from 0.93 MPa to 0.66 MPa and 0.64 MPa, MOR from 16.2 MPa to 10.6 MPa and 12.1 MPa, MOE from 1246 MPa to 1573 MPa and 1466 MPa, and increasing of TS from 6.7% to 7.1% and 6.0%, respectively, when isocyanate adhesive was used. The similar changes were showed when the density of particleboard was 0.75 g.cm-3. Improving density of particleboard appropriately and decrease density difference between the surface to chip layers could make the profile density curve tend to be stable, which could get a relatively high mechanical strength and water resistance. Synergistic effects between isocyanate and fire retardants was confirmed. The particleboard prepared with isocyanate was obviously superior to that prepared with MUF resin in all performances.

Some mechanical properties of densified and laminated Lombardy poplar (Populus nigra L.)

In this study, it was studied the effects of densification and then lamination processes on some mechanical properties of Lombardy poplar (Populus nigra L.), which is one of the low density tree species. Densification temperatures were 80, 100, 120 and 140ºC and ratios of densification were 15, 30 and 50 %. Furthermore, lamellas with a thickness of 4 mm cut from densified materials were laminated by bonding one on top of the other with urea formaldehyde (UF) and polyvinyl acetate (PVAc) adhesives. Bending, modulus of elasticity, compression and tensile tests were applied by preparing specimens from the pieces. According to test results, the most suitable temperature level was 120°C. As the ratio of densification was increased at this temperature level, increase were observed in the mechanical properties. Also, lamination provided significant increases in the mechanical values compared to laminated but undensified Lombardy poplar. Increases were observed in the mechanical properties reaching 444 % with application of densification and lamination processes.

Longitudinal glued joints of timber beams and the inf luence of quality manufacturing onto their carrying capacity

The content of this article is to analyse destructive testing results of longitudinal solid wood joints of structural size beams with internal and external glued wood-based panels (plywood) stressed in bending, which was mostly focused on simulating the effect of the glued line thickness (1 and 3 mm) and the influence of contact surfaces of longitudinally connected elements when bending loads. The aim of this article is to compare the carrying capacity and the joint real behaviour under load with values obtained using numerical modelling and calculation according to valid standards.

Strength of corner and middle joints of upholstered furniture frames constructed with black locust and beech wood

Great interest is attracted lately in the utilization of Black locust (Robinia pseudoacacia L.) timber large quantities that are expected to be harvested and enter the market next years, since this species was included in the proposed and financed species for cultivation by the European Union. This study was carried out to evaluate the strength of the two most frequent joints in the upholstered furniture frames, constructed with black locust, using also beech wood (Fagus sylvatica L.) for comparative reason. In the specific research, the joints of mortise and tenon and double dowel were selected to be used and were constructed both in corner and middle joints, using two adhesives (PVAc and PUR). Bending moment capacity of the joint specimens was investigated, as well as the coefficient of elasticity of each joint.

Analysis of composite action of various mass timber structural panels with concrete layer

In the presented paper composite actions of various mass timber panels with concrete layer are compared. The composite action of timber and concrete by grooves in wood and by adhesive was realized. In the frame of experimental investigation bending test of real scale composite panels with cross-laminated and nailed/glued vertical planks mass timber was performed. In the analysis, vertical mid-span deflection of tested panels was compared and also some technological aspects of their production were taken into account.

Cadhesive bond performance of heat- treated fir wood (Abies borrissiregis)

The thermal treatment of wood leads to chemical, structural and natural changes in the wood components which can significantly affect the adhesive bond performance of the wood in various ways depending on the type of adhesive that is used. In the present research, fir wood (Abies borrissiregis) was undergone thermal treatment at 180°C, and 200°C for 3, 5 and 7 hours. Two different types of adhesives were used for the adhesive bond: polyurethane (PUR) and polyvinyl acetate PVAc. During all the wood treatment conditions, higher endurance in the bonding shear strength was noticed for the non-modified samples and the shearing strength by compression load was decreased while the thermal treatment was becoming more intense. Generally, while the PVAc bond shows better performance during the adhesion and higher modulus of rupture in comparison with the polyurethane PU after the thermal treatment of the wood.

Bond performance of formaldehyde-based resins synthesized with condensate generated during kiln-drying step of wood

This research investigated the potential use of condensate generated during vacuum drying with high frequency of wood in the synthesis of urea-formaldehde (UF) and melamineformaldehyde (MUF) resins. The liquid condensate (5 wt%) of total resin composition) of walnut, beech or oak was replaced with deionized water used in the synthesis of UF and MUF resins. The condensate did not affect the properties of the UF and MUF resins in terms of density, solid content, viscosity, pH, and gel time as compared with the control resins. The control UF and MUF resins did not show a significant difference with the bond strength of UF and MUF resins at dry and wet conditions, except for the oak-UF resin. As for the dry condition, the control resin had the highest bond strength with a value of 12.9 N. mm-2, followed by beech-UF resin (12.6 N. mm-2), walnut-UF resin (12.1 N. mm-2), and oak-UF resin (11.8 N. mm-2), respectively. A similar trend was observed for the wet condition. All the modified UF and MUF resins complied with the minimum requirements of EN 12765 standard at dry and wet conditions. The results of this research can be useful for environmentally friend solution of the waste condensate discarded to the ground water.