پانته آ عمرانی

Nowadays, in metropolitan areas, principled and hygienic waste management is very important. Recycling is one of the most appropriate options in waste management. Hereof, the present study was aimed to investigate the possibility of using textile waste fibers in the manufacture of Medium Density Fiberboard (MDF).

This experimental study was performed on lab-scale. Fabric waste was prepared by separation method at source from a clothing manufacturer in Tehran and converted into fibers. Test boards were made with weight percentage of mixing textile waste fibers to industrial fibers at three levels of 0:100, 10:90 and 15:85, respectively, 10% urea-formaldehyde adhesive, with 16 mm thickness and 0.7 g/cm3 density by hot press. Then, properties of the boards were measured including bending strength, modulus of elasticity, internal bond, hardness, water absorption and thickness swelling. The results were analyzed with ANOVA test.

The results of ANOVA showed that the effect of textile waste fibers on the bending strength, modulus of elasticity and swelling thickness of 2 and 24 hours of boards made at 5% probability level was significant. Additionally, the highest values of physical and mechanical properties are related to made boards with 10% of textile waste fibers.

The results showed that it is possible to make MDF with textile waste fibers. The use of wastes such as fabrics in the production of new functional products can be considered as one of the strategies to reduce waste and thus to maintain human health and the environment.

The aim of this research was investigating the effect of fiber reinforced polymer (FRP) on the strength of T-shaped wooden joints under tension load. In this regard, T-shaped joints were constructed with beech and poplar species and were reinforced with 1 and 2 layer of carbon and glass fibers reinforced epoxy and vinylester polymers of composite. Joint members were assembled by used of wooden dowels and polyvinyl acetate adhesive and then withdrawal resistance of reinforced joints were studied. Results of variance analysis showed that the independent effect of species of joint members, resin type and number of fiber layers at FRPs was significant at 5% level. Results have indicated that withdrawal resistance of joints constructed with beech species was more than the poplar species. The investigation of the effect of number of layers showed that the withdrawal resistance of the joints reinforced by two layers of carbon and glass fibers was more than one layer. Results of FRPs investigation indicated that use of epoxy matrix in comparison with vinyl ester matrix exhibited better results. In addition, carbon fibers have shown better performance than glass fiber as reinforcing agents. According to the results the best treatment was the joints of beech wood and reinforced by composites with epoxy matrix and reinforced with two layers of carbon fibers.

The aim of this study was investigation of the performance of mitered corner joints (L-shaped) reinforced by fibers reinforced polymer (FRP) at maximum stress area under diagonal compression loading. In This way, structural performance of constructed corner joints of two species of beech and fir reinforced by fiber reinforced polymer at polymeric matrix of epoxy with one and two layer of carbon and glass fibers and were investigated. After construction of the mitered joints with wooden dowel and polyvinyl acetate adhesive, the joints were reinforced with FRP composites and then were subjected to diagonal compression loading. Results have indicated that reinforcing layers prevent joint opening, however, failure was occurred at the joint by peeling fibers from wood surface or members fracture near the joints by stress concentration. The results of variance analysis showed that the independent effect of species of joint members and numbers of fibers layer were significant at 95% confidence level. The results showed that use of beech wood in comparison with fir wood, composites reinforced by carbon fibers compared to glass fibers, as well as the use of two layers of fiber compared to 1 layer of fibers, exhibited better performance in constructed joints. The joints made with beech wood and reinforced with 2 layers of composites reinforced by carbon fibers showed the best performance under diagonal compression loading.

Fiber Reinforced Polymer (FRP) has become one of the most popular methods in the reinforced, repair and rehabilitation of structure due to its ease of application and the special physical characteristics. Both destructive and nondestructive assessments have been used to test the characteristics and durability of FRP in order to investigate the condition of the structure. The aim of this research was to investigate the structural performance of corner joint reinforced with fiber reinforced polymer (FRP) composite under diagonal tension load. Constructed joints from two wooden species of beech (Fagus orientalis) and fir (Abies alba), were reinforced with reinforced composites of one and two layer of carbon and glass fibers and then they were tested under diagonal tension load. The miter corner joints were made with wooden pin and polyvinyl acetate adhesive. The fibers lay-up was done manually. Epoxy resin was used as a polymeric matrix. Result of investigation indicated that use of beech wood in comparison with fir exhibited better results. In addition, glass fibers have shown better performance than carbon fiber as reinforcing agents.  Inspection of diagonal tension specimens after failure have indicated that using of FRPs on the surfaces of L-shaped miter prevent joint opening, however, failure was occurred at the joint by increasing of load and vertical displacement and the general wood weakness in tension perpendicular to the grain and shear parallel to the grain at dowels site due to stress concentration. Also the results showed that the miter corner joint made with beech species and two layers of glass fibers had the highest stress carrying capacity.

The aim of this study is to investigate withdrawal resistance of T-shaped joints made of wooden biscuits. Biscuit joints which also called plate joints are usually constructed from compressed solid beech wood. Biscuits in the joints take up the moisture from water-based glues and resulted swelling at the slot leads to appropriate and strong joint. The variables of this study were the species of joint members including beech (Fagus orientalis) and fir (Abies alba), biscuit size of 10 and 20 (1 biscuits per joint) and type of glue including Polyvinyl acetate (PVAc), Polyurethane (PU) and Urea formaldehyde (UF). After constructing the specimens, withdrawal resistance test of biscuits was carried out. The results showed that the effects of independent variables namely, the species of joint members and the type of glue on the withdrawal resistance of biscuit joints was significant in the 1% level, but the independent effect of biscuit size was not significant. Also the results showed that the withdrawal resistance of the joints made with beech species was higher than fir. The polyurethane adhesive exhibited the best performance in comparison with the other adhesives. Finally, the best performance of the joints made with biscuit (beech, biscuit size 10 and polyurethane glue) was compared with the wooden dowel joints, which former showed the higher withdrawal resistance.

The aim of this study is to investigate the performance and fracture monitoring of dowel-welded joints by micrographs of scanning electron microscopy (SEM). In this regard, joints with hornbeam (Carpinus betulus) and fir (Abies alba) members were constructed by using hornbeam smooth and grooved dowels with diameter of 10 and 12 mm. The joint members were cut according to EN 326-1 standard and after assembling, the joints were subjected to the tensile test according with EN 319 standard. The results showed that effects of independent variables on tensile strength was significant. The investigation of the scanning electron microscope images from the fracture zone of the welded joint member demonstrated that not only the fracture at the joint zone was not occurred, but also the welded area between the dowel and the joint member exhibited greater strength in comparison with wooden members during tensile loading. Also, the investigation of the image obtained from the SEM showed that the components of the welding line did not remain on the dowels with smooth surface, and the dowel surface was also affected by micro cracks, but the surfaces of grooved dowels were sound and part of the welding line was observed on the dowels. According to the results of this study, compared to conventional adhesives, using of welding in making joints with small diameter and smooth dowel, not only provides a joint with the proper structural performance, but also it provides optimum utilization of wood in making joint. This leads to raw materials savings, cost reduction of raw materials preparation and reduction of jointing time which altogether cause to reduce production costs.

This study was conducted to evaluate the stress carrying capacity of miter corner joints made with binder of biscuit under diagonal tension and compression loading. Corner joints with the Joint members from two species of beech (Fagus orientalis) and Fir (Abies alba), with 1 to 2 biscuits to size of 10 and 20 and with help adhesives of polyvinyl acetate (PVAc), polyurethane (PU) and urea formaldehyde (UF), they were made and tested. Since wooden pin joint is one of the most commonly included furniture joint, the test specimens were constructed using a pin and PVAc adhesive as a control for comparison with binder of biscuit. The results of analysis of variance showed that the independent effect of the species of Joint members, the size of biscuits, the number of binders and the type of adhesive in both compression and tensile loading is significant at 5% level. The results showed that the stress carrying capacity of the joints made with beech species is higher than that of fir species, and with increasing size and number of biscuits, the stress carrying capacity increases. The stress carrying capacity of the joints made with the polyurethane adhesive was also higher than those made joints with polyvinyl acetate and urea formaldehyde adhesives. The stress carrying capacity of the joints made under compression load was greater than the stress carrying capacity under the diagonal compression and tension load. The highest stress carrying capacity was observed in joints made with beech wood, two binders, biscuit size 20 and polyurethane glue, in both diagonal tension and compression loading.

Joints in furniture and wooden structures due to the highly sensitive bearing load are today one of the most important scientific topics. The most recent method proposed to build wooden joints in Europe and the United States is a method eco-friendly, without using any type of adhesive substance or connector, called "wood welding". In the present study, the effect of diameter and dowel surface on the tensile strength of softwood joints (made with dowel) was investigated using two wood welding and glue bonding. Polyvinyl acetate glue (PVA) for bonding, species Fir (Abies alba) for members joint and species Hornbeam (Carpinus betulus) for connector dowels were selected as fixed parameters. The structure of the welded surfaces was analyzed using scanning electron microscopy (SEM). The results of the tensile strength test showed that parameters of diameter and type of dowel surface have a significant effect on the tensile strength of softwood joints in both joint methods.

The insertion of dowels into solid wood for furniture has been used for centuries. Recently, this simple technology has been upgraded. The objective of the research was to evaluate and compare the tensile strength of the joints made of wood dowel through new method “wood welding” and classical method “using of glue”. Variables included dowel joints method (welding joint and joint with glue), dowel diameter (10 and 12 mm) and dowel surface (smooth and grooved). Members joint and dowel wood were hornbeam species (Carpinus betulus) and the used glue was polyvinyl acetate (PVA). The results showed that the types of joints, diameter and surface dowel, have significant effect on the tensile strength, so that welded joints, dowel diameter 12 mm and dowel grooved surface has the most tensile strength to other samples. The results also showed that in all cases, the strengths of the joints made by welding was more than the joints made by PVA glue.

The goal of this study was to investigate effects of wood species (Beech and Fir)، number of connectors (1 and 2)، size of biscuit (10 and 20) and type of adhesives (Polyvinyl acetate (PVAc)، polyurethane (PU) and urea-formaldehyde (UF)) on bending moment resistance of joints fabricated with biscuit. Results have shown that member of joint، number of connector، size of biscuit and type of adhesive had significant effect on the bending moment resistance. Bending moment resistance of joints made of Beech wood were stronger than joints made of Fir ones. Bending moment resistance has increased، with the increase of size and number of biscuit. Performance of joints with PU adhesive had better than PVA and UF. Highest bending moment resistance were obtained from joints glued with PU adhesive، size of biscuit 20 and 2 connectors. The results also indicated that joints made with biscuit and glued with PU had higher resistance than wooden dowel joints.