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Wood Matters – A celebration of the work of John R. Barnett

REACTION WOODS

INSPIRATION FOR SMART MATERIALS

AND STRUCTURES

George Jeronimidis

CompressionWood

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WHAT IS INTERESTING ABOUT REACTION WOODS ?

IS THERE SOMETHING USEFUL TO LEARN ?

INSPIRATION FOR ENGINEERING SOLUTIONS

CONCLUSIONS

Reaction wood is used by trees to modulate shape of trunk and branches

Why aren’t all trees the shape of weeping willows ?

Adaptive shape change

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Wood Matters – A celebration of the work of John R. Barnett

Wood microstructure

20-30m

Fibres provide the key organisational elements for functional self-assembly

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Wood Matters – A celebration of the work of John R. Barnett

Creating functional fibre architectures in plant cell walls

Barnett & Jeronimidis, 2003Clair, 2001

Cave, 1980

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Wood Matters – A celebration of the work of John R. Barnett

Physical interactions between cell walls during maturation

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Wood Matters – A celebration of the work of John R. Barnett

Hygro- or thermal expansivity of angle-ply structures

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Wood Matters – A celebration of the work of John R. Barnett

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

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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Non-symmetric laminate

De-hydration / Maturation

Shape change (curvature)

normal wood

tension wood

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Wood Matters – A celebration of the work of John R. Barnett

Differences between reaction wood and normal wood provide mechanism for shape change

Coutand et al, 2004

Poplar – Normal Wood Poplar – Tension Wood

Inspiration for engineering solutions

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Wood Matters – A celebration of the work of John R. Barnett

Adaptive roof element

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Wood Matters – A celebration of the work of John R. Barnett

Tension or Compression Wood “Cell” element

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Wood Matters – A celebration of the work of John R. Barnett

“Tissue / Organ” element

Tension wood side

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Wood Matters – A celebration of the work of John R. Barnett

Tension wood side

Compression wood side

Element combining “tension” and “compression” wood

Stretching-Bending

Different materials

Different scale

Different actuation

…………………………….but

SAME FUNCTIONALITY

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DIFFERENTIATION AT THE “MATERIAL” LEVEL

(Anisotropy, Heterogeneity, Hierarchies)

FUNCTIONAL INTEGRATION AT THE “SYSTEM” LEVEL

+DIFFERENTIATION AT THE “STRUCTURE” LEVEL

(Shape, Dimensions, Geometry)

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Wood Matters – A celebration of the work of John R. Barnett

Conclusions

THANK YOU JOHN FOR THE INPIRATION AND SUPPORT DURING ALL THESE YEARS

YES !!! IT IS ONE OF YOUR PICTURES

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Wood Matters – A celebration of the work of John R. Barnett