This document summarizes research on using wood modification technology to produce high-strength engineered wood composites. Wood modification techniques like viscoelastic thermal compression can increase wood strength and stiffness 3-4 times by densifying it while minimizing cell wall damage. Composites made of modified wood laminated with adhesive have greater strength and stiffness than traditional composites or solid wood. The document outlines how modified wood from various fast-growing species can be used to manufacture structural composite materials for applications like construction and transportation. It presents research demonstrating improved bonding and mechanical properties of composites made with modified wood laminates. Challenges include controlling dimensional stability and preventing brittle failure, but the technology offers opportunities to utilize lower quality wood for high-value

1. Frederick A. Kamke1, Josef Weissensteiner 1,2
and Hongling Lui 1,3
1 Oregon State University, Corvallis, Oregon USA
2 Universität für Bodenkultur , Vienna, Austria
3 Northwest A&F University, Yangling, Shanxi, P.R. China
Forest Products Society 65th International Convention
June 19-21, 2001, Portland, Oregon

2. Abstract
Wood modification technology has created opportunities to expand
the application of structural wood composites. Previously, wood
composites had mechanical properties that were limited by the
properties of the virgin wood. Typically, properties of the composite,
such as OSB, plywood, and LVL, are less than the properties of the
virgin wood due to process-induced damage or limitations of adhesive
bonding. However, composites have the advantage of reduced
variability, and consequently, engineering design values for the
composite are often greater than comparable solid wood products.
Wood modification technology can increase strength and stiffness of
wood three to four times above virgin timber. While wood modification
increases processing cost, strategic composite design minimizes final
product cost by minimizing the amount of modified wood required. In
addition, modification techniques may upgrade low quality veneer that
previously was not suited for structural composites. This presentation
summarizes applications of wood modification technology in the
design of a laminated composite.

3. Manufacture high value composite materials from
rapid-grown, under-utilized and sustainable forest
resources.
11-year hybrid poplar
Courtesy of APA The Engineered Wood Association

4. Densification of wood by mechanical compression
into thin lamina using rapid processing technology
and lamination to produce engineered composites.
• Damage of wood during densification
• Dimensional stability
• Adhesive bonding
• Manufacturing cost

5. Densification of wood by mechanical compression
into thin lamina using rapid processing technology
and lamination to produce engineered composites.
• Wood densification
• Thermo-mechanical compression
• Thermo-hydro-mechanical (THM) compression
• Viscoelastic thermal compression (VTC)
• And others

6. Manufacture structural composite materials from
rapid-grown and sustainable forest resources. I-Beams
Bridge Structures
Transportation Vehicles
Structural Panels
Laminated
Engineered Wood Concrete Forms
Veneer Lumber
Flooring
Wind Turbine Blades

7. • Perpendicular to grain
• Wood above glass transition temperature
• Minimal to no cell wall fracture
• Can be performed in a few minutes

8. • Radiata pine (Pinus radiata)
• Loblolly pine (Pinus taeda)
• Douglas-fir (Pseudotsuga menziesii)
• Western hemlock (Tsuga heterophylla)
• Alaska cedar (Chamaecyparis nootkatensis)
• Yellow-poplar (Liriodendron tulipifera)
• Aspen (Populus tremuloides)
• Sweetgum (Liquidambar styraciflua)
• Paulownia (Paulownia tomentosa)
• Eastern Cottonwood (Populus deltoides)
• Hybrid poplar clones (Populus sp.)
• Maple (Acer sp.)
• Red oak (Quercus rubra)

9. Green Building Materials Laboratory

10. Sealed Chamber
Max. Steam Pressure: 150 psi
Max. Compression: 3000 psi
Platen Size: 10 in. x 24 in.
Stainless-Steel
Bellows, 28 in Ø
Interior: Electrically-Heated Platens with Water Cooling

11. Electrically-Heated &
Lid Sample Water Cooled Platens
Steam Vent
Inlet
Thermal Insulation Stainless-Steel Bellows
SIDE VIEW of CHAMBER

12. Typical Process Schedule
TEMPERATURE 170oC
WOOD THICKNESS
<10 mm
COMPRESSION
FORCE 800 psi
TIME
125 psi
STEAM
PRESSURE
CONDITIONING TIME COMPRESSION TIME COOLING TIME

13. Example: Hybrid Poplar - Effect of Compression Time
UNTREATED

14. Number of plies = 16
Non-VTC MOE = 11 GPa
VTC MOE = 25 GPa
LVL MOE = 15 GPa
2 VTC Plies
38.1 mm
14 Non-VTC Plies
2 VTC Plies
30% increase of MOE with 25% VTC by weight

15. 100 95 Hybrid Poplar &
Phenol-Formaldehyde
Effective Adhesive
Penetration (mm)
80
60
41
40
30
23
20
0
0 63 98 132
Densification (%)
Kutnar et al (2008) Wood and Fiber Sci. 40(3):362-373

16. Example: Hybrid poplar
ASTM D905
Shear in
Compression
Loading

17. 3-Point Bending
UNTREATED
UNTREATED • Brittle failures common
• No delaminations

18. F
Specific Gravity: Untreated = 0.37, VTC = 1.2 D
h
Hybrid Poplar
HB = F / (p  D  h)
D = 10 mm
F = 500 N (112 lbf)
Rautkari, Kamke & Hughes, 2011, Wood Sci. & Tech.

19. F
Specific Gravity: Untreated = 0.37, VTC = 1.2 D
h
Hybrid Poplar
HB = F / (p  D  h)
D = 10 mm
F = 500 N (112 lbf)
Rautkari, Kamke & Hughes, 2011, Wood Sci. & Tech.

20. Design by Corvallis Tool Company
Annealing Zone
Cooling Zone
Conditioning Zone
Compression Zone

21. • Densification possible without cell wall fracture.
• Thin lamina may be processed in short time.
• Energy cost approximately same as conventional
veneer processing by substitution of drying step.
• Densified wood bonds well and consumes much less
adhesive.
• Dimensional stability controlled by heat treatment or
chemical treatments, if needed.
• Brittle failure could be a problem in critical structural
applications.
• Manufacturing cost higher than conventional veneer
processing, but significant value added in process.

22. USDA Wood Utilization Research Center Special Grant
JELD-WEN Foundation
Oregon BEST