59 Table 15 The increasing percentage of dynamic MOE, static MOE, MOR,
density, SMOE and SMOR value of 3 mm and 5.25 mm LVL of poplar cultivars made of juvenile and mature veneers
Table 16 The increasing percentage of dynamic MOE, static MOE, MOR and density value of 3 mm and 5.25 mm LVL of douglas-fir made of
juvenile to mature veneers Dynamic
MOE Mpa
Static MOE Mpa
MOR MPa
Density kgm
-3
LVL 5.25mm
Mature 14899
14202 65
573 Juvenile
13651 13222
59 514
gain in +9
+7 +15
+11 LVL 3mm
Mature 15061
14834 60
596 Juvenile
13321 12148
54 532
gain in +13
+22 +11
+12 Density 561 + 45 kgm
-3
of douglas-fir LVL made of 3 mm veneers had a significantly higher density 542 + 42 kgm
-3
than LVL made of 5.25 mm. The thicker veneer used to produce LVL would result in lesser glue line compare to
LVL from thinner veneer. This lesser glue line would cause a lower density of LVL. The same with poplar, douglas-fir LVL made of thicker veneer were
significantly lighter 4 on average when each process parameter was constant Table 16. This result was different from Palka 1961 who found that Douglas-
fir plywood from 2.54 mm veneer has the lowest density compare to 3.6 mm and 5.1 mm veneers. However, these results were in line with several results in the
literature H’eng et al. 2010; Daoui et al. 2011; De Melo and Del menezzi 2014.
4.7.2 Modulus of Elasticity MOE
4.7.2.1 Static MOE The ANOVA Appendix 1, showed that juvenility, poplar cultivar and
veneer thickness had a significant influence on poplar static MOE p0.01. In Appendix 2, ‘Brenta’ had the highest value of static MOE 9439 MPa, while
‘I214’ had the lowest 6713 MPa. Duncan’s multiple comparison test Appendix 2 show that the MOE static
value for mature poplar LVL 8880 MPa was statistically higher than for juvenile poplar LVL 7664 MPa. It also shows that there was a statistical difference
Dynamic MOE
MPa Static
MOE MPa
MOR MPa
Density kgm
-3
SMOE MNmkg
-1
SMOR MNmkg
-1
LVL 5.25mm
Mature 9431
9104 54
400 22.7
0.136 Juvenile 8126
7736 45
390 19.8
0.115 gain in
+16.1 +17.7
+20 +2.6
+12.8 +15.4
LVL 3mm
Mature 9233
8769 55
417 21.0
0.132 Juvenile 8174
7628 47
412 18.5
0.115 gain in
+13.0 +15.0
+17.0 +1.2
+11.9 +12.9
60 between cultivars which could be mostly attributed to wood density. Indeed, r
2
between static MOE and density reached 0.6, while between MOR and density reached 0.7 when using data from Appendix 3.
Duncan’s multiple comparison test Appendix 2 shows that the poplar MOE static values for 3 mm and 5.25 mm are statistically different. It is interesting to
note that for such a large number of samples, the effect of the veneer thickness on MOE was not negative since the average MOE increased from 8202 MPa for 3
mm to 8416 MPa for the 5.25 mm veneer. Figure 38 shows that the static MOE values between 3 mm and 5.25 mm LVL were well correlated R
2
=0.7 but this link was highly dependent on the cultivar. Furthermore, the use of thicker veneers
could reduce adhesive consumption, and simplify and accelerate the production of panels with their high mechanical properties.
Figure 38 Correlation between 14 poplar cultivars static MOE of LVL made of 3 mm and 5.25 mm veneers in flatwise direction
The ANOVA Appendix 1 shows that the sample position factor in poplar did not have a significant effect on static MOE. Mean flatwise static MOE 8267
MPa was not statistically different from the mean edgewise MOE 8279 MPa. MOE is measured in a zone of pure bending local modulus EN408. This is why
the MOE values between flatwise and edgewise positions were quite the same. Different from the results of Bing measurements for which shear deformation was
considered. Shear deformations are different since shear modulus differs due to wood orthotropy and slightly to lathe check orientation. This is also the expected
reason why some differences in MOE can be seen in Appendix 3.
The ANOVA and Duncan’s multiple comparison test results in poplar were in agreement with observations in the literature regarding the effect of juvenile
wood on solid wood and LVL stiffness Kretschmann et al. 1993; Kretschmann 1997; Nazerian et al. 2011.
ANOVA Appendix 4 shows that, juvenility and interaction between juvenility and veneer thickness had significant effect to static MOE of douglas-fir
LVL p0.01. Average value of douglas-fir static MOE are presented in Appendix 5. Static MOE 14484 + 2204 Mpa of LVL made of mature veneers
was significantly higher compare to that of LVL made of juvenile 12735 + 1574 Mpa. This result was in line with Kretschmann et al. 1993 who concluded that
the ratio of juvenile to mature of Douglas-fir LVL is approximately 0.8.
y = 0.99x + 203.16 R² = 0.73
6000 6500
7000 7500
8000 8500
9000 9500
10000
6000 7000
8000 9000
10000 Static
MO E
L VL
3 m
m
Mp a
Static MOE LVL 5.25mm Mpa
