Josef Füssl, Markus Lukacevic, Josef Eberhardsteiner
Institute for Mechanics of Materials and Structures
WKO– TheFutureof Building2018,08.05.2018
Three trends in mechanical modelling of materials
Motivation
Demands:
à Stabilityà Structural safetyà Serviceability
Design methods:
à Static methods16. Jhd da Vinci, Galilei 17. Jhd Bernoulli, Newton18. Jhd Euler19. Jhd Ritter
à Numerical methods20. Jhd Zienkiewicz
Building Structure Material
Material behaviour:
à Material model17. Jhd Hooke 18. Jhd Coloumb19. Jhd Mohr
à Material propertiesstiffness, strengthviscosity, ...
à ExperimentsTensile-,compression-,Bending tests
Design methods:
à Analytical methods20. Jhd. Eshelby20. Jhd. Mori, Tanaka21. Jhd. ???
à Numerical methods20. Jhd Zienkiewicz
à Timeà Moneyà Less informationVariability of “nature”
Complexity of model
First: Looking into the microstructure of materialsWood
MicroCT Scanning Electron Microscope
Atomic Force Microscope
Different scales of observation, with different material phases and different morphologies
First: Looking into the microstructure of materialsFired clay
MicroCT SEM-EDX / NI Atomic Force Microscope - SThM
Material behaviour of certain material phases
Second: Mechanical linking of these scales up to the product scale
lpolynet=20 nm
Zellulose
lcwm=0.5-1 µm lHW=2-4 mm
CMM, Mori-Tanaka Unit Cell Method CMM,
Mori-Tanaka
lT≈lR=20-40 µm
Composite Cylinder Assemblage
lcellulose=10 nm
amorpheZellulose
kristallineZellulose
Wasser
LHC-Komplex
CMM, Mori-Tanaka
Multiscale model for wood
Second: Mechanical linking of these scales up to the product scale
Mechanical behaviour of material as function of its microstructure (morphology, behaviour of material phases)
Input: wood species (microstructural characteristics), density, moisture content
Output: macroscopic stiffness and strength behaviour for specific wood sample
Multiscale model for wood
0
5
10
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25
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0 0.5 1 1.5 2 2.5 3 3.5
F [N
]
s [mm]latewood
earlywood
TR configuration
§ Finite Element modellate-/earlywood modeledhomogeneouslywith new multisurface crack criteria
§ Micro-wedge-splitting testsfor RT and TR configurations[Frühmann2003, Keunecke2007]
Third: Implementation of non-linear material behaviour into design concepts
0
5
10
15
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25
30
0 0.5 1 1.5 2 2.5 3 3.5
F [N
]
s [mm]
TR configuration
Third: Implementation of non-linear material behaviour into design concepts
0
5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3 3.5
F [N
]
s [mm]
TR configuration
Third: Implementation of non-linear material behaviour into design concepts
0
5
10
15
20
25
30
0 0.5 1 1.5 2 2.5 3 3.5
F [N
]
s [mm]
TR configuration
Third: Implementation of non-linear material behaviour into design concepts
0
5
10
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25
30
0 0.5 1 1.5 2 2.5 3 3.5
F [N
]
s [mm]
TR configuration
First crack
Maximum load
Third: Implementation of non-linear material behaviour into design concepts
Plastic zones
GLT with hole underbending
Realistic simulation considering plasticity and cracking
Third: Implementation of non-linear material behaviour into design concepts
Bending load:Unit cell representation:
Example: Cross-laminated timber (CLT)
Third: Implementation of non-linear material behaviour into design concepts
Realistic mechanical behaviour of products
Summary
Necessary information to …
First: Looking into the microstructure of materials
Second: Mechanically linking the microstructural scales up to the product scale
Third: Implementation of non-linear material behaviour into design concepts
Realistic predictions of mechanical behaviour
Efficient optimisation and improvement of materials
Potential for targeted development of new products
HHOHOTowerVienna,84Meters,24Stockwerke [cetus Baudevelopment GmbH]
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