Blockboard is mostly used when there is lengthy piece of wood is required which makes furniture stiffer or and prevent it from bending. While using Blockboard always take care that core of Blockboard runs length wise to achieve maximum strength.
Block board is commonly available in the following sizes in market 1. In fact, production of panels can be encouraged due to the technical feasibility of using short length core blocks which should maximize yield from low-grade and scrap wood in the manufacturing of three-ply face-glued blockboard. In this way, the veneering and gluing process provide efficient use of forest resources via producing panels from low-grade wood logs with small dimensions Colak et al.
To produce acceptable panels from short wood slats spliced together endwise used in the core layer, the role of strip joint type on the mechanical performance of blockboard coated with different wood species must be evaluated.
The result showed that the type of joint in a layer, different species veneers and the adhesive spread had great effect on properties of bonded products. Simultaneously, if it is assumed that blockboard is the one type of laminated particleboards which in slats form core layer, properties of panels can be affected by different wood species of veneers after the lamination process Nazerian In fact, hardwood and softwoods, both as species groups and as species within a group, have different porosity.
This causes variation in the amount and direction of adhesive penetration Vick The influence of tensile and compression loading on the strength of corner V-nail and dovetail joints, with and without adhesive were studied for fiberboard and particleboard Taghiyari et al. It was determined that V-nails are recommended for craftsmen in case adhesive is used.
However, dovetail joints provide higher strength if the production process necessitates not to use adhesive in joints. Effectiveness of finger jointing in utilizing mango wood sections for various end uses like furniture was evaluated Kumar et al. It was found that the modulus of elasticity of the sections joined showed significantly better values than that of unjointed clear wood sections. Under compression, the parameters of the jointed sections were either similar or better than those of the unjointed clear wood sections.
It was demonstrated that physical and mechanical properties of coated panel can be improved with different coatings Norvydas and Minelga , Nemli et al. According to Nazerian , the bending strength is correlated to the wood veneer species covered panels, and consequently, to the adhesive penetration and to the amount of adhesive applied on the veneer surface and the panel.
The literature had only limited information on the feasibility of using low-cost solid wood in blockboard panel production. Moazami and Nazerian investigated the effect of end-to-end joint types of short slats on the modulus of rupture and modulus of elasticity of the blockboard.
It was determined that the type of joint had the effect on the modulus of rupture MOR and modulus of elasticity MOE , significantly, so the panels having short slots jointed with end-to-end half lap joint in core layer had the highest strength properties.
According to Morrell , blockboard manufacturing facilities to use low-cost solid wood strips that may contain defects undesirable for the face of the finished panels and to produce lower cost utility types of boards. Besides, one of the main advantages of blockboard over others laminated wood products such as plywood is that the core layer of the board is made up of thick sections of wood.
Accordingly, application of few number of thick layers or slats in core reduces cost and manufacturing time Laufenberg et al. The aim of this study was to determine the effects of joint type of athel wood slat used in core layer, veneer wood species coating core layer and resin type used in glue line on the bending strength of blockboard.
The core layer consisted of athel Tamarix aphylla slats. Grain orientation on cross section of core layer slats was parallel to the growth rings. The prepared end-to-end jointed slats used in the core layer of samples are shown in Figure 1. Figure 1: Three types of end-to-end joints used in core layer of the blockboard. Three specimens were each prepared with slats parallel to the outer layers Figure 2 a and three specimens with slats perpendicular to the outer layers Figure 2 b.
Figure 2: Specimens with slats a parallel to the outer layers and b perpendicular to the outer layers for the bending strength test. Density mean values, compaction ratio and density profile of samples before and after gluing process and press are shown in Table 1 and Figure 3. Table 1: Density mean values and compaction ratio of samples before and after press.
In blockboard production, slats and veneers are laminated together under pressure. Although, the same processing conditions were chosen in press, with respect to different species of wood veneers used in outer surfaces and different compaction ratio of panels created during the press, board densities and their profiles were varied Figure 3.
Figure 3: Density profile of panels veneered with fir, beech and oak. When a panel was veneered with fir, the tendency to increase in density was more significant than with beech and oak. Similarly, the compaction ratio of panels veneered with fir was higher than others. With respect to that, the thickness of the panels with the pressure applied depending on wood species, the reason for this stronger tendency to increase the density is related to the thickness loss of these panels due to the compression rate during hot pressing, and also an increase in resin-to-wood ratio.
To determine the effect of end-to-end joint type on the bending strength of panels, the bending strength of slats connected with three type of end-to-end joints butt joint, mitered joint and half lap joint was examined Table 2. Table 2: Modulus of rupture of athel slats jointed with different end-to-end joints used in core layer of blockboard. MOR of the tested slats fluctuated from 23 to 40MPa. Slats jointed with half lap joint showed a higher MOR values 40MPa , while samples jointed with butt joint showed the lowest value 23MPa.
These results are in conformance with the studies in the literature River , Kapica The sample jointed with mitered joint showed intermediate value 27MPa. A multifactor variance analysis results displaying whether there are any differences between the modulus of rupture MOR values is given in Table 4.
Table 4: Statistical analysis of bending strength of blockboard produced with different variables. Therefore, it may be possible to manufacture stronger boards by favorable choice of variables involved in this study.
It means that the bending strength of blockboard is indeed highly depended on the loaded direction to the grain of face plies. Testing perpendicular to the grain orientation of face plies showed a significantly lower MOR than those tested parallel to the grain orientation in dry condition.
This could be attributed to the fact that the bending strength of wood massive along the grain orientation is higher than across the grain orientation. This could be due to the fact that glue distribution was not as uniform during the panel production. The edges of both blockboard and laminboard are unattractive and cannot be cleaned up well. Place softwood strips, veneers or fill and paint the edges. Blockboard and laminboard may be bought with a variety of applied finishes such as wood veneers and plastic laminate surfaces.
If both sides are treated in the same way blockboard and laminboard have a good resistance to warping. Sources : -Laminboard looks very similar to blockboard but it is made up of softwood strips, mm in width as opposed to blockboard, which has strips of 25mm.
In both cases the strips are sandwiched between two outer veneers with the grain running at right angles to the core strips. The facing veneers may be birch.
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