Properties of Rubberwood LVL reinforced with Acacia
Author(s)WONG, Ee Ding; RAZALI, Abdul-Kader; KAWAI, Shuichi
Wood research : bulletin of the Wood Research Institute Kyoto
University (1996), 83: 8-16
Type Departmental Bulletin Paper
KURENAI : Kyoto University Research Information Repository
Properties of Rubberwood LVL reinforced
with Acacia Veneers*l
WONG Ee Ding*2, RAZALI Abdul-Kader*3
and Shuichi KAWAI*2
(Received May 31, 1996)
Abstract--The properties oflaminated veneer lumber (LVL) [15-ply, 3.6 mm veneer thickness]
produced from Acacia mangium (Mangium) thinnings, Hevea brasiliensis (Rubberwood) and their
combinations were investigated.Melamine urea formaldehyde (MUF) was used as the binder.
In the species combination, Mangium veneers were incorporated in the tension and compression
zones (i.e., top and bottom layers) ofthe LVL, with Rubberwood veneers in the core.
two Rubberwood: Mangium combination ratios were studied, i.e., 3: 2 and 1: 2.
LVL reinforced with Mangium exhibited, a lower degree of bow compared to pure Rubberwood
LVL. The LVLs were evaluated in accordance with the Japanese Agricultural Standard for'
Structural LVL (1993).All of the LVLs passed ,the cold water soak and boiling water
delamination tests.Similar dry shear strength was registered by all of the LVLs, with shear
retention of 58 to 63% after cyclic boiling;LVL with higher proportion of Mangium recorded
higher shear strength retention.Modulus of elasticity (MOE) was found to increase with
increasing Mangium plies in the faces. This is'reflected by 2 and 12% MOE increment in LVL
reinforced with 3 and 5 plies ofMangium, respectively.
not seem to improve the m o d u l u ~ of rupture (MOR), but 13% MOR increment was recorded by
incorporating 5 plies of Mangium.Rubberwood and 3-ply Mangium reinforced LVL met the
minimum requirements stipulated for 80E Special Grade, while the 5-ply Mangium reinforced LVL
made the 100E Special Grade. Mangium LVL passed the l20E Special Grade.
The effects of
Reinforcement using 3 Mangium plies did
Key words: Laminated veneer lumber, reinforced, Hevea brasiliensis, Acacia mangium, melamine urea
The previous study has shown the technical feasibility to produce structural grade
laminated veneer lumber (LVL) from Rubberwood (Hevea brasiliensis) and Mangium (Acacia
mangium) using phenol formaldehyde (PF), melamine urea formaldehyde (MUF) and urea
formaldehyde (UF) as the binders!).Except where UF was used as the binder, Mangium
LVL generally had higher shear strength compared to Rubberwood LVL.
bending, Mangium LVL registered higher modulus of elastic (MOE) and modulus of
rupture (MaR) than Rubberwood LVL, irrespective ofresin type.
In term ofstatic
The uniformity ofboth
*1 This paper was presented at IUFRO XX World Congress, 6-12 August 1995, Tampere, Finland.
*2 Laboratory of Structural Function.
*3 Golden Hope Fibreboard, P.O. Box 10, 71807 Nilai, Malaysia.
WONG et ai.: Properties of Rubberwood LVL reinforced with Acacia Veneers
physical and mechanical properties ofsolid wood has been improved through processing into
It has been demonstrated that combination of different wood specIes III vanous
proportions would provide wood composites with properties differing from those based on
Product engineering in composite manufacture enables optimal utilization
of the existing resource, as wood elements of varying grades, qualities or types could be
placed in various zones to produce composites with "tailored" properties.
engineered profile may take the form of placement of high quality veneers at the surfaces,
and low grade veneers in the inner plies.Since the Mangium LVL were found to have
In LVL, this
superior strength properties compared to Rubberwood LVL in the earlier work, it is
therefore the object ofthis study to investigate the properties of l5-ply LVL fabricated using
mixtures of Rubberwood and Mangium.
2.1 Raw materials
Two plantation species, i.e., Mangium and Rubberwood were used.
Mangium thinnings were obtained from Batu Arang Forest Plantation, Selangor, whereas
the matured 25-year old Rubberwood were supplied by rubber estate holders to a plywood
mill in Cheras, Kuala Lumpur.
The ten-year old
The logs were bucked to about 132 cm length.
removed manually, while debarking was not done for Rubberwood logs.
peeled to 3.6 mm thick veneer on a 4-foot Meinan lathe using varying peeling speed.
The tough bark of Mangium was
Both species were
2.2Fabrication of LVLs
The LVLs were manufactured on a newly installed LVL line which has yet to start
commercial production.Low quality Rubberwood veneers (virtually all were round-up
veneers marred by tapping wounds, pin holes and sap stain) were used.
veneers used were fairly tight and smooth with rather high incidence ofloose knots (less than
2 cm in diameter).
In order to avoid excessive veneer waviness, Rubberwood veneers were dried to about
15% moisture content (MC), while Mangium veneers were dried to less than 6% MC, at a
temperature of l50-l70°C. The 1,219 mm long veneers were end-jointed using scarfjoints
of 1 : 3 slope to a length of 2,438 mm.These joints were randomly staggered throughout
the LVL to reduce the weakening effect. Melamine urea formaldehyde (MUF) was applied
to the 1,219X 2,438 mm veneer using roller coater.
side facing tight-side and loose-side facing loose-side.
species LVL were produced. In LVL with species combination, the effects of two
Rubberwood: Mangium combination ratios were studied, i.e., 3 : 2 and 1 : 2, where equal
The veneers were assembled with tight-
Fifteen-ply mono-species and mixed
WOOD RESEARCH No. 83 (1996)
number of Mangium veneers (3 and 5 plies) were placed in the tension-compression zone,
i.e., top and bottom layers, with 9 and 5 plies of Rubberwood in the core.
time was limited to less than 30 min. Cold pressing at 10 kgf/cm2specific pressure was
applied for 20 min, followed by hotpressing at 125°C under specific pressure ofl2 kgf/cm2
for about 50 min.
2.3 Evaluation of LVLs
Evaluation of the LVLs produced were based onJAS (1993) for Structural Laminated
Veneer Lumber. All the test specimens were conditioned under controlled relative
humidity and temperature of 65±5% and 21 ±2°C, prior to testing.
Six test specimens of 75X 75 mm were prepared from each sample for water soak test
(24 h water soak followed by 24 h oven dry at 60± 3°C) ; andboiling water delamination t e ~ t
(5 h boiling water immersion followed by I h cold water soak, and 24 h oven dry at 60±.
3°C), respectively. The thickness swelling and water absorption were measured after 24 h
The shear specimens were cut to 40 mm width with length of six times the thickness.
The load was applied perpendicular and parallel to the veneer faces for flatwise and
edgewise bending, respectively, at a constant rate ofabout 150 kgf/cm2/min.
test, the specimens were tested after cyclic boiling, i.e" 4 hboil followed by 20 h oven dry at
60± 3°C, with another 4 h boil and I h cold ~ a t e r soak, and shear tested when the specimens
were still wet.
Two specimens of width 90 mm and length 23 times. the thickness were prepared for
flatwise and edgewise 4-point bending tests, respectively.
In wet shear
3.1 .Physical properties of LVLs ..
3.1.1 Dimensional property
Upon removal from the hot press, no obvious warping was observed in the LVLs.
However, some degree of bow was noticed in the 50X90X2,438 mm LVL beams, after
conditioning to about 10% MC. Mono-species Rubberwood LVL registered 8 to 22 mm
deviation from the neutral axis, while incorporation of Mangium veneers in the faces
significantly reduced the deviation to Q-4 mm.
3.1.2 Density and moisture· content
Based on the respective veneer density of 0.64 and 0.56 g/cm3, Rubberwood and
Mangium LVLs with densities of0.65 and 0.61 g/cm3recorded a densification of2 and 8%,
respectively.As reflected by the thicknesses of veneer and LVL, thickness reduction in
both Mangium (~%)
and Rubberwood(l-:-2%) correlates well to the respective degree of
densification.The low densityjuvenile Mangium veneer was obviously more compressible
WONG et at.: Properties of Rubberwood LVL reinfbrced with Acacia Veneers
compared to the high density matured R u b b ~ ~ ~ o o d .
Mangium v e n e ~ r at Rubberwood: Mangium ~ a t i o s of 3 : 2 and I : 2 reduced the LVL
density from 0.65 g/cm3in Rubberwood l VI'. ~ o 0.63 and 0.62 g/cm3, respectively (Table 1).
The MC of the LVL produced r a n . ~ ~ d from 8 to 10%.
3.1.3Thickness swelling and water absorption
Rubberwood is more hygroscopic than Mangium.
LVL using Mangium could reduce water absorption by 40-58%, and the resultant thickness
swelling was significantly lower (Table I).
Cold water soak delamination test (24 h cold water soak f o l l ~ U r e d by 24 h drying at 60±
3°C) did not result in any delamination in all the LVL.
h followed by 1 h cold water soak and drying at 60±3°C for 24 h gave rise to less than 4%
delamination in the LVL samples.
Incorporation of lower density
Reinforcement of Rubberwood
While soaking in boiling water for 5
Mechanical properties of LVLs
Melamine urea formaldehyde (MUF) was found to bond well with both Mangium and
The mean dry shear value of the reinforced Rubberwood LVL declined
slightly with increasing proportion of Mangium (Table 2).
flatwise shear samples failed in Rubberwood core during shear bending, the dry shear
strength of the reinforced Rubberwood LVL was similar to that of Rubberwood LVL.
the edgewise shear bending, 54% of the samples experienced failure across laminae, while
Since most (70%) of the
Table 1.Density and moisture content of veneer and LVL
D e n s i ~
+ 9-ply Rubberwood
+ 3-ply Mangium
+ 5-ply Rubberwood
+ 5-ply Mangium
Note: * 75 X 75 mm sample size, after 24 h water soak, ** Based on 15-ply Rubberwood LVL, a and bare
means of 10 and 4 specimens, respectively.