REACTION WOODS

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REACTION WOODS INSPIRATION FOR SMART MATERIALS
AND STRUCTURES
George Jeronimidis
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• WHAT IS INTERESTING ABOUT REACTION WOODS ?
• IS THERE SOMETHING USEFUL TO LEARN ?
• INSPIRATION FOR ENGINEERING SOLUTIONS
• CONCLUSIONS

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Adaptive shape change
Why arent all trees the shape of weeping willows
?
Reaction wood is used by trees to modulate shape
of trunk and branches
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Fibres provide the key organisational elements
for functional self-assembly
20-30 mm
Wood microstructure
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Creating functional fibre architectures in plant
cell walls
Barnett Jeronimidis, 2003
Cave, 1980
Clair, 2001
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Physical interactions between cell walls during
maturation
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Interesting effects result from coupled
deformations in anisotropic laminated
structures Neither component in the laminate
(fibres / matrix) has a negative or zero thermal
exapansion coefficient Yet, the laminate can be
designed to have negative or zero expansivity for
some specified fibre angles
Hygro- or thermal expansivity of angle-ply
structures
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Depending on the microfibrillar orientation in
the various cell walls and their relative
thickness, their interactions during maturation
can produce axial shrinkage, axial expansion,
radial shrinkage, radial expansion and
twist Axial contraction in tension woodAxial
expansion in compression wood
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Partial or total suppression of deformation
(twist) due to cell-cell adhesion high internal
stresses at interfaces
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Differences between reaction wood and normal wood
provide mechanism for shape change
Non-symmetric laminate
Shape change (curvature)
De-hydration / Maturation
Poplar Normal Wood
Poplar Tension Wood
Coutand et al, 2004
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Inspiration for engineering solutions
Adaptive roof element
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Tension or Compression Wood Cell element
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Tension wood side
Tissue / Organ element
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Compression wood side
Tension wood side
Element combining tension and compression
wood
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Stretching-Bending
Different materials Different scale Different
actuation .but
SAME FUNCTIONALITY
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Conclusions
DIFFERENTIATION AT THE MATERIAL LEVEL
(Anisotropy, Heterogeneity, Hierarchies)

DIFFERENTIATION AT THE STRUCTURE LEVEL
(Shape, Dimensions, Geometry)
FUNCTIONAL INTEGRATION AT THE SYSTEM LEVEL
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THANK YOU JOHN FOR THE INPIRATION AND SUPPORT
DURING ALL THESE YEARS
YES !!! IT IS ONE OF YOUR PICTURES