booosting 20 jaar vooruit! jubileum oktober 2008 sybrandvd_zwaag
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April 9, 2023 1
Sybrand van der Zwaag
Faculty of Aerospace Engineering
TU Delft
Delft Centre for Materials
Self Healing : an alternative strategy to make materials
perform better
Booosting 2008 Rotterdam
April 9, 2023 2
Material development over 120 centuries
After M.F. Ashby
April 9, 2023 3
General characteristics of man-made (structural) materials
• All material processing chains geared towards putting the atoms/molecules at the right place and to make them stay there.
• We improve properties by design principles aimed at avoiding initial (production) damage and/or damage formation during use.
• i.e. we work with DAMAGE PREVENTION only
April 9, 2023 4
Time
Pe
rfo
rma
nc
e
• Time dependent degradation
• Cracking
• Ingress agressieve substances
lessons from nature ?
April 9, 2023 5
More lessons from nature
April 9, 2023 6
50 µm
Cells to remove material
Cells to create material
Cells to sensethe stress-
state
Assuring a dynamic equilibrium in bone
April 9, 2023 7
?,,, control parameter: P =
cellactivity
OC
OB
OC > OBBone mass
P
OB > OCBone mass
P
setpoint
Cell activity during remodelling
April 9, 2023 8
The 3 key ingredients of self healing materials
• most structural units are there to perform the desired mechanical function
• some structural units are mobile to perform self healing at damaged sites
• some structural units are capable of sensing the damage
April 9, 2023 9
Time
Performance
original
improvement
SH coating
Self Healing ambitions (single event)
April 9, 2023 10
Self healing ambitions (multiple healing)
Time
Performance
original
improvement
SH coating
April 9, 2023 11
Self healing ambition : massive and small scale damage
Time
Performance
original
improvement
SH coating
April 9, 2023 12
Self Healing behaviour
An ideal self healing material:
• Repairs the damage for 100 %
• Repairs itself an infinite number or times
• The repair is autonomous• The material has better
properties than the classical material it replaces
• Is cheap• Is used by architects
A minimal self healing material
• Repairs the damage by 5%
• Repairs itself only once
• Needs an external stimulus
• Has poorer properties than the classical material it replaces
• Is expensive
• Is used by aerospace engineers
April 9, 2023 13
Drivers for self healing materials
1. High repair costs (e.g. subsurface structures)
2. High reliability (e.g. aircraft, installations)
3. Surface quality (e.g. painst and coatings)
4. High degree of irritation when repairs take place (e.g. road repairs)
April 9, 2023 14
Self healing in building materials
Victor Li (2005)
April 9, 2023 15
self-healing mechanisms in concrete
• Can occur in both flow and non-flow through cracks
• Requires ample supply of carbonates and calcium ions (more common in flow through cracks)
• Interaction of water and concrete achieve passive self healing
Air = CO2
CO2 H2CO3
CO32-
CO32- + Ca2+
Concrete
Crack
Ca2+
Water
ConcreteWater Crack
CO32- + Ca2+ CaCO3
CaCO3
C. Edvardsen (1999)
April 9, 2023 16
Metal-like Behavior of Engineered Cementitious Compound
0 1 2 3 40
1
2
3
4
5
6
Cra
ck
Wid
th (m
)
Stress
Str
es
s (M
Pa
)
0
20
40
60
80
100 Crack width
Strain (%)
20
mm
Damagecu ~ 4%
Victor Li, Michigan, USA
April 9, 2023 17
Self-Healed ECC Specimens
3 mm 3 mm
Before Self-Healing After Self-Healing
w ~ 60m = 1.5%
Formation of CaCO3
April 9, 2023 18
Mihara Bridge in Hokkaido, 2004
Cable Stayed BridgeHokkaido, JapanCompleted: Oct., 2004Open to traffic: April, 2005Length: 1000 m, span: 340 mDeck area: 20,000 sq. m.; ECC layer thickness: 38 mm
Composite ECC-Steel DeckECC used for stiffening deck & decrease stress in deck steelFRP shear key appliedWeight reduction 40%Cost reduction: 50%Expected service life: 100 yrs
April 9, 2023 19
Self Healing bridge in Amsterdam
van Hees, TUD
April 9, 2023 20
Bacteria Stimulated Crack Healing in Concrete
Delft Centre for MaterialsH.M. Jonkers, Microlab, TU Delft
April 9, 2023 21
Endospores
Alkaliphilic Endospore Bacteria
April 9, 2023 22
Goal:
- Self-healing (blocking / plugging) of cracks results in more durable concrete- Use bacteria that produce bio-minerals (e.g. calcite)
Methods:
- Create right conditions for bacteria to1. survive concrete environment for long time2. produce calcite upon water ingression through cracks
- Characterize self-healing of cracks:1. type of material deposited2. blocking characteristics 3. (regained) mechanical properties
April 9, 2023 23
Zonder Metbacteriën
CaCO3-kristallen
Bacterial formation of CaC03 crystals
on concrete fracture surfaces
Jonkers, TU Delft
April 9, 2023 24
Preferred concrete properties:
7. Self-healing!
Impregnation techniques to image the effect of healing
April 9, 2023 25
Why self-healing concrete?
The Corrosion Society (USA) estimates the annual direct cost of corrosion
in construction and other applications to be $276 billion.
Longer service life, less maintenance: saves money and the environment
April 9, 2023 26
Self healing in coatings
April 9, 2023 27
Polymer coating structure
topcoat
basecoat
primer
substrate
April 9, 2023 28
Maintaining Performance in natural materials
April 9, 2023 29
Human Skin detail
April 9, 2023 30
Self healing via a liquid agent
“The Scott White concept”
April 9, 2023 31
The Scott White approach
= epoxy = liquid adhesive capsule = catalyst
S.R. White et al, Nature 2002
April 9, 2023 32
Just cracked
April 9, 2023 33
5 seconds later
April 9, 2023 34
1 minute later
= crosslinking adhesive
April 9, 2023 35
45 minutes later
= fully crosslinked adhesive
April 9, 2023 36
Self-Healing Epoxy
2.5 wt% Grubbs catalyst5 wt% microcapsules
Healing conditions:room temperature, 48 h
= 90.3%
K Ichealed
KIcvirgin
April 9, 2023 37
Encapsulation approach in a coating
• PU coating with DCPD capsules/Cat in Wax• Fraunhofer IFAM; Farbe & Lack, 10, 35-41 (2007)
April 9, 2023 38
• www.small-journal.com
• Small 2007, 6• (926-943)
April 9, 2023 39
Coating on Micro vascular substrate
Kathleen S. Toohey, Nancy R. Sottos, Jennifer A. Lewis, Jeffrey S. Moore & Scott R. WhiteNature Materials 6, 581 - 585 (2007)
April 9, 2023 40
Molecular Approach to Self Healing in coatings
April 9, 2023 41
Molecular processes in reversible networks(Diels –Alder reactions)
O
R
N
O
O
R'O
R
N
O
O
R'
CH3
C CH2
O
O O
O
O
CH2C
CH3
n m
N
O
O
R
O
O
N
+
Diels Alder reaction
N
O
O
OR
O
O
O
N
N
O
O
O
R
O
O
O
N
N
O
OO
R
OO
O
N
N
O
OO
R
OO
O
N
N
O
O
O
R
O
O
O
N
N OO
O
R
O
OO N
+
April 9, 2023 42
Self healing coatings based on hydrogen bonding
April 9, 2023 43
The future is nearer than you may think
April 9, 2023 44
Concluding remarks
1. Self healing behaviour explains the survival of
Roman buildings and structures
2. Self healing behaviour is a valuable property
for modern building materials
3. It is a challenge for architects to make full use
of the self healing potential of future materials