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Bog'liq
Edward Le PhD Dissertation

Density (g/cm
3
)
MO
E
 (
MP
a
)
HROM
1/Dt=0
1/Dt=0.02
Figure 6.21. Simulated modulus versus overall panel density for different reciprocal of 
interfacial stiffness parameter in commercial OSB. 
Figure 6.22 is the simulated modulus for panels with VTC strands in the surface 
(from previous study in chapter 3, section 3.6.4) versus overall density for two different 
values of 1/D
t
. MOE increased as density increased. In Figure 6.21, the simulated MOE 
is lower than the HROM even with the case of 1/D
t
=0. This is because surface VTC 
strands are higher in stiffness and also aligned with the grain, thus contribute to the 
calculation of MOE.
Unlike the results in Figure 6.21, here the density of VTC strand already higher 
than the core. Therefore less compaction on the face strands. This results in no crossover 


147 
like the case in Figure 6.21 at high compaction. Furthermore, there are all VTC strands 
on the face layers with high stiffness thus contributed the most to the modulus.
The results of Figure 6.22 also show interfacial effects have a large contribution 
to the overall stiffness of the panel. There is linear increase of the stiffness as a function 
of compaction.
6000
7000
8000
9000
10000
11000
12000
13000
14000
15000
0.50
0.55
0.60
0.65
0.70
0.75
0.80
Density (g/cm
3
)
MO
E
 (
MP
a
)
HROM
1/Dt=0
1/Dt=0.02
Figure 6.22. Simulated modulus versus overall panel density for different values of 1/D
t
for commercial OSB with surface VTC strands. 
6.7 Summary and Conclusions 
The vertical density profile influences the overall OSB panel stiffness. In 
processing, the manufacturer usually demands higher density at the surface to carry the 
higher load in bending for structural applications. To know the specific density profile at 
different levels of compaction, manufacturers could benefit from optimization during 
processing and manufacturing of OSB. During processing, manufacturers usually obtain 
the stiffness and vertical density profile by trial and error. From the relationship between 


148 
vertical density profile and stiffness at different levels of compaction, the manufacturer 
can tailor the process to achieve high load carrying panels. Moreover, enhanced strand 
(VTC) on the surface layer increases density.
Additionally, reducing yield stress of the surface strands in 2D simulations gave 
an increase in density for the face. Reducing yield stress and moduli at the face layers in 
2D increases the density at the surface area. In 2D, reducing moduli at the surface layers 
had more effect on the density profile than reducing the yield stress. Furthermore, 
increasing compaction rate increases the density at the surface of the panel.
The simulation of density profile in 3D showed different results than the 2D. In 
3D, the Poisson’s expansion resulted in no increase in density of the surface. There is 
some increase in density of the surface when there is no gap on the surface layer. Unlike 
the 2D, there is no increase in density profile of the surface when reduced yield stress of 
the surface strands. However, in 3D reducing moduli at the surface layers had an effect 
on the density profile of the surface strands. Furthermore, 3D model of MPM is able to 
look into interior structure or morphology of the panel.
Finally, to fully model the vertical density profile, moisture content gradient and a 
temperature profile is needed. A better plasticity model to account for densification is 
needed because the traditional plasticity model did not allow for plastic densification 
after yielding occurred. As all results all densification is due to by elastic deformation. 
Additionally, the simulations may need to be done on 3D. More work is needed to get the 
same simulation results for the vertical density profile as experimental results.

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