Thermo-hydro and thermo-hydro-mechanical wood processing: An opportunity for future environmentally friendly wood products

Figures & data

Table I. Sugar analysis of aspen before and after heat treatment with saturated steam at 220°C in a closed system for 8 minutes (Rowell et al. 2009).

	Before heat treatment	After heat treatment
Weight loss (%)	0	2.2
Arabinan (%)	0.56	0.20
Galactan (%)	0.68	0.58
Rhamnan (%)	0.30	0.14
Glucan (%)	42.4	42.2
Xylan (%)	16.3	14.6
Mannan (%)	1.6	1.5
Total carbohydrate (%)	61.8	59.2

Figure 1.  Bending of bows from a facsimile of a wall painting in the tomb of the nomarch Amenemhat at Beni Hasan, ca. 1971–1928 B.C. A nomarch was the semi-feudal ruler of an Ancient Egyptian province (Newberry 1893)

Figure 2.  Stress-strain (σ–ϵ) diagrams for air-dried non-plasticized beech and plasticized beech. Note that the strain axis has different scales to the right and to the left of the origin (after Prodehl 1931a,b). MC, moisture content

Figure 3.  Various modes of deformation of the cell walls of wood under compression in the longitudinal direction; (a) plastic deformation of the cell wall (formation of slip planes), (b) lateral buckling of the cell walls, (c) localised shearing band, (d) diffuse buckling of the cell walls

Figure 4.  Diagrammatic representation of the mechanisms of local deformation of wood cells under a longitudinal compression force; (a) wood before the application of the force, (b) collapse of fibre by rupture, (c) collapse by the buckling of cell walls

Figure 5.  Micrograph of uniformly densified spruce latewood cells after compression at 140°C under saturated moisture conditions (Navi and Heger 2005). Micrograph of the boundary between the compressed surface and uncompressed regions of wood (Inoue et al. 1990)

Figure 6.  Schematic illustration of wood densification in the transverse direction at the cell level, recovery and different methods of fixation of the compression set: (a) initial undeformed state, (b) softening of the wood by steam, (c) densification, (d) cooling, (e) total set recovery, (f) mechanical fixation, (g) chemical fixation or fixation by a THM treatment

Figure 7.  Movements, velocities and forces in four different types of frictional welding; (a) linear friction, (b) orbital friction, (c) circular friction and (d) rotary friction welding (Stamm 2005)

Figure 8.  Cross-sectional profile of a dowel ligno-bonded by rotary friction welding (Ganne-Chédeville et al. 2005)

Figure 9.  Micrograph of a zone of joined and adjacent areas between two pieces of spruce welded by circular friction (Stamm et al. 2005a)

Figure 10.  A wooden multi-layer element made of alternate layers of spruce and beech bonded by circular friction welding (Stamm 2005)

Figure 11.  Compwood machine for pre-compression of wood in the longitudinal direction to make it bendable in a cold state (view from above). The operations are: (a) loading, (b) autoclave for plasticizing the wood, (c) automatic input, (d) machine for longitudinal compression, and (e) output of densified wood

Figure 12.  Thermo-hydro-mechanical apparatus and the internal moulding block (left) and transformation of a circular trunk to a square-section block by two-dimensional densification (right) (Ito et al. 1998a)

Figure 13.  Wood tube of densified spruce (left) and filament winding of moulded tubes (right)

Figure 14.  Manufacture of wooden tubes from (a) sawn wood and (b) a log

Figure 15.  Moulding of a densified wood panel to a tube of diameter 450 mm; (a) charging, (b) closing, (c) forming. The thickness of the tube wall is 100 mm

Rowell , R. M. , Ibach , R. E. , McSweeny , J. and Nilsson , T. 2009 . Understanding decay resistance, dimensional stability and strength changes in heat treated and acetylated wood . Wood Material Science and Engineering , 4 : 14 – 22 . doi: 10.1080/17480270903261339

 Google Scholar

Newberry , P. E. 1893 . Archaeological Survey of Egypt, Part I. Beni Hasan , Edited by: Griffith , F. L. London : Kegan Paul, Trench, Trübner & Co Ltd. .

 Google Scholar

Prodehl , A. 1931a . Zur Holzbiegetechnik [About the wood bending technology] . Zeitschrift des Vereines deutscher Ingenieure , 75 : 1217 – 1222 .

 Google Scholar

Prodehl , A. 1931b Untersuchungen über das Biegen gedämpften Holzes [Studies on the bending of steamed wood]. PhD thesis , Sachsischen Technischen Hochschule zu Dresden .

 Google Scholar

Navi , P. and Heger , F. 2005 Comportement thermo-hydromécanique du bois [Behaviour of thermo-hydro-mechanical processed wood] (Lausanne, Switzerland: Presses polytechniques et universitaires romandes) .

 Google Scholar

Inoue , M. , Norimoto , M. , Otsuka , Y. and Yamada , T. 1990 . Surface compression on coniferous wood lumber. Part I. A new technique to compress the surface layer . Mokuzai Gakkaishi , 36 : 969 – 975 .

 Web of Science ®Google Scholar

Stamm , B. 2005 Development of friction welding of wood –physical, mechanical and chemical studies . PhD thesis No. 3396 , Ecole Fédérale de Lausanne , Switzerland .

 Google Scholar

Ganne-Chédeville , C. , Pizzi , A. , Thomas , A. , Leban , J.-M. , Bocquet , J.-F. , Despres , A. and Mansouri , H. 2005 . Parameter interactions, two-block welding and the wood nail concept in wood dowels welding . Journal of Adhesion Science and Technology , 19 : 1157 – 1174 . doi: 10.1163/156856105774429037

 Web of Science ®Google Scholar

Stamm , B. , Natterer , J. and Navi , P. 2005a . Joining wood by friction welding . Holz als Roh- und Werkstoff , 63 : 313 – 320 . doi: 10.1007/s00107-005-0007-6

 Web of Science ®Google Scholar

Ito , Y. , Tanahashi , M. , Shigematsu , M. and Shinoda , Y. 1998a . Compressive-molding of wood by high-pressure steam-treatment: Part 2. Mechanism of permanent fixation . Holzforschung , 52 : 217 – 221 . doi: 10.1515/hfsg.1998.52.2.217

 Web of Science ®Google Scholar