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Part II Modeling Drying of Three Dimensional Pulp Molded

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									Composite Panel Products for Stage Scenery




                  John F. Hunt, P.E.
             Research Mechanical Engineer
     USDA, Forest Products Laboratory, Madison, WI, USA




       2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
      Overview



Wood Composite Panels
Wood and Moisture
Effects of Moisture on Panel Properties
Comments




           2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
       Wood Composite Panels




Chapter 10 from the Wood Handbook
www.fpl.fs.fed.us


             2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
Wood Composite Panels
     Wood Composites
Wood-based Composite
Panels come in a variety of
configurations giving various
performance properties.




           2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
All Plywood
Panels are
not equal.

Plywood
Properties
by Species




              2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
Wood Composite Panels
Wood Composite Panels




   2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
Wood Composite Panels
Wood Composite Panels
Wood Composite Panels
          Wood Composite Panels
                                   Sheathing         Sheathing         Particle-         MDF     Hardboard
                                   Plywood             OSB              board

Linear hygroscopic                  0.15%             0.15%             0.35%            0.35%    0.35%
expansion
Bending
 Modulus of Rupture (MPa)         20.7–48.3         20.7–27.6         3 – 23.5           14 -    31 – 41.2
                                                                                         34.5
 Modulus of Elasticity (GPa)      6.89–13.1         4.83–8.27        0.5 - 2.75          3.45
Tensile Strength (MPa)            l0.3–27.6          6.9–l0.3                                      15.2
Compression Strength (MPa)        20.7–34.5          6.9–l0.3
Shear Through Thickness
 Shear Strength (MPa)               4.1–7.6          6.9–l0.3
 Shear Modulus (GPa)             0.47–0.761         1.24–2.00
Shear In-Plane
 Shear Strength (MPa)               1.7–2.1          1.38–2.1
 Shear Modulus (GPa)              0.14–0.21         0.14–0.34
                     2005 USITT Conference & Stage Expo, Toronto, CA March 16-19, 2005
        Wood and Moisture
 Wood takes on
 moisture slowly
but also gives up
 moisture even
    slower.
      Wood and Moisture


Determining the
moisture content
of a piece of wood
from relative
humidity and
temperature
measurements.
      Wood and Moisture


Determining the moisture content of a piece of wood from
painting. For example, if 1 gallon of paint with 40% solids
were painted at a rate of 1gallon/200ft^2.

Then for:
Hardboard: approximately 2% absorption of water into the
face of the panel (½ to the board ½ to evaporation).
Particleboard: approximately 0.5% absorption of water into
the face of the panel (½ to the board ½ to evaporation).
     Comments
If possible stand panels on their side for a short period
of time to all equilibrium moisture absorption.

If possible apply similar coatings to both sides to
prevent warping.

For some panels warping is a wood problem and may
be difficult to over come.

Cyclic moisture warping effects will occur on a set due
to daily air-conditioning settings and heating due to
lighting or other sources.

								
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