Tree biomechanics

Tension in the outer part

Compression in the inner part

When cutting dead tree —> gwoth stresses relieve

Generated during the differentiation process of cells in the cell wall formation process

Cellulose tension hypothesis: Bilden von Cellulose --> einzelne Ketten --> wenn Ketten assembliert werden zu fibrillen --> Teilkristallinie teile --> führen zu verkürzung --> übt Zugkraft aus

Lignin swelling hypothesis: Swelling in the cell wall due to insertion of lignin —> pushing the cellulose fibers apart

Unified hypothesis: Combine the 2 others

Each cell generated by cambium has the same level of streses

Stress in older cells is removed a bit by newer cells

tension in outer part (1/3) tension, inner part compression

No stresses in radial direction

Radial: interaction of longitudinal and tangential stresses

Tangential: Compression in the peripherie

Longitudinal tensile stress in the periphery is essention to protect the side of the stem, which is under compression during wind loads

A small radial compression stress on the cambium is essential for regular wood formation

Tangential compression at the periphery —> wound closure by the cambium

SW: Compression wood

HW: Tension wood additional G-layer (MFA 0)

Challenge: create a system which is stiff an deformable at the same time