Background Karakteristik Retak Kupas And Kekasaran Permukaan Finir Kayu Cepat Tumbuh Dan Pengaruhnya Terhadap Laminated Veneer Lumber
2 Currently, the more promising EWP is Laminated Veneer Lumber LVL which
knows a very strong development worldwide Tenorio et al. 2011. LVL is different from solid lumbers. It is made of natural veneers which are bonded
together by adhesives. The veneers are firstly peeled from hardwood or softwood logs and then dried. Compared with solid lumber, LVL have more advantages: 1
less lumber defect rotted knots, cracks and other defects because the common lumber defects have been dispersed during production Ranta-Maunus 1995;
Daoui et al. 2011; 2 stable in dimension and more resistant to warp, twist, bow, and cup Harding and Orange 1998; Kamala et al. 1999; Erdil et al. 2009; 3
available in large dimensions LVL can be as long as 8000 mm, as thick as 300 mm, as wide as 1200 mm Erdil et al. 2009; 4 high elastic modulus and bending
stress Erdil et al. 2009.
However, the production of high quality LVL using fast growing wood species would be faced against two main problems: 1 presence of important rate
of juvenile wood, transition age between juvenile and mature wood being often close to harvesting age Kretschmann et al. 1993; 2 veneer surface quality
surface roughness, thickness variations and lathe checking Rohuma et al. 2013; Darmawan et al. 2015; 3 the drawback of LVL is that the part of the glue inside
can reach important ratio until 20 Daoui et al. 2011. Moreover, the presence of formaldehyde still has to be taken under consideration. These criterias might be
able to be minimized by careful application of boiling treatment on fast growing wood species having high portion of juvenile wood.
Due to the shape of fast growing species logs are round, straight and cylindrical, recently, fast growing species in Indonesia and France, have been
rotary cut for laminated-wood products. However, as fast growing species are being peeled and much more juvenile woods are being utilized, severe lathe check
veneer would undoubtedly be produced and manufactured DeVallance et al. 2007; Darmawan et al. 2015. Therefore, it considerably needs to study lathe
checks of veneer peeled from those fast growing species. The risk of this checking can be reduced by using a nosebar Kollmann et al. 1975. However,
recent spindle less rotary lathes, which are widely used to peel small log diameter of fast growing wood species, have not been completed with an adjustable nosebar.
A boiling treatment of bolts would be considered to reduce the lathe check Kabe et al
. 2013; Darmawan et al. 2015. Based on the research conducted by Pugel et al. 1990, juvenile wood can
be utilized to produce composite products flakeboard, particleboard, fiberboard. Kretschmann et al. 1993 also reported that it is possible to make LVL from
juvenile wood veneer. One of the most significant technical advantages of laminated veneer lumber LVL is that specific performance characteristics can be
considered in its design Wang et al. 2003. By strategically placing selected veneer sheets within the composite, it is possible to manufacture a wood-based
product that has well-controlled physical and mechanical properties.
The effect of veneer quality especially lathe checks on glue-bond quality, modulus of elasticity MOE and modulus of rupture MOR during laminated
veneer lumber LVL production should be also important to be studied. DeVallance et al. 2007, reported that a high frequency of lathe checks results in
lower strength. It is due to the increasing of lathe check on the veneer would lead to lower glue-bond quality and bending strength MOE and MOR.
3 Measurements of bending test MOE and MOR could be performed by
using dynamic and static modulus of elasticity. Using various species of wood, sample dimensions and growth conditions, several studies have shown a strong
linear correlation between the dynamic and static modulus of elasticity Biblis et
al . 2004; E
l- Haouzali 2009
. However
, the use of such methods for estimating the MOE of engineered wood products, particularly LVL, has not been widely applied.
To the best of our knowledge, only Daoui et al. 2011 used
a vibrating method with limited success.
By considering the above issues and references, the research topics proposed were 1 determination of demarcation pointtransition age between juvenile and
mature wood; 2 the effect of juvenility on veneer lathe check and surface roughness of fast growing wood species; 3 the effect of lathe check and juvenility
on fast growing wood species LVL glue bond and bending strength; and 4 determination of sengon and jabon LVL specific modulus of elasticity by
modelling peeling an evolution of raw material properties on segmented ring basis.
Hypothesis that were proposed in this study were as follow: 1.
Some traits could be used to determine the demarcation pointtransition age between juvenile and mature wood on fast growing species
2. Juvenility would affect lathe check and surface roughness, and boiling
treatment would decrease lathe check and surface roughness 3.
Lathe check and juvenility would influence glue bond strength and LVL bending properties
4. An analytical model should be used to determine the variation of specific
MOE LVL values from pith to bark