advanced materials and material characterization€¦ · · 2014-08-05advanced materials and...

Advanced Materials and Material Characterization

Part 2: Advanced Materials

Prof. Dr. H. P. Strunk

Master Materials Science course in 1st and 3rd semesterWS 2013/14

Chapter 3

3.0 Outline

3. Biological materials, concepts, principles

3.1 Biological materials: product/remains of living cells by reactions and/or metabolism

wood, bone, tooth, silk, resilin

3.2 Biomimetic materials: artifical materials purposely produced

functional surfacesmimiking nacre (shell)

3.3 Biological concepts: preparation of artifical materials to imitate propertiesoptimized by nature

self cleaning (lotus effect), minimization of resistance (shark and dolphin skin), maximization of attachment force (insects, reptiles, gecko)

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line split intoplants, fungi,mamals

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The materials scientist's view onearth history:

Cryogenian Period850–635

great extinction

065

150

200

275

400

465

500550


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first plants on land

Cambrian explosion

insects, plants withwoody stems

dinosaursammonites

mineralizedexoskeletontrilobites

archeopterix

great extinction

The materials scientist's view onearth history:

cynodonts

first bones in jawless fish


time line for thedivergence of animals, plants, and fungi. This treehas a radial time scaleoriginating about 1100 million years (my) ago withthe last common ancestorof plants, animals, and fungi. Contempo-raryorganisms and time are at the circumference. Lengths of branches arearbitrary. The order of branching is establishedby comparisons of genesequences. The times of the earliest branchingevents are only estimates, since calibration of themolecular clocks isuncertain and the earlyfossil records are sparse.

Cell Biology 2nd edition, by Thomas D. Pollard, William C. Earnshaw, and

Jennifer Lippincott-Schwartz

Elsevier, 2007, e-book

great extinction

065

150

200

275

400

465

500550


3.0 Outline


3.0 Outline

first plants on land

Cambrian explosion

insects, plants withwoody stems

dinosaursammonites

mineralizedexoskeletontrilobites

archeopterix

great extinction

The materials scientist's view onearth history: materials specifications

bones light weight, highlymechanically resistant

bones stable high load bearing

teeth friction resistant, hard

organic, hard, sturdy, highly elastic fibersflexible but mechanicallystable layered structures

hard with limited flexibility

cynodonts

first bones in jawless fish


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3.0 Outline

Classifications

Preparation Structure and Physics Properties

Methods of preparationby‐product due to pH changesdead end product of metabolismHybrid materials

Task of the master course'Nano‐Compound Materials'

next summer semester(Prof. Bill)

our job now mostly mechanical properties

electrical/optical propertiesonly every now and then,

otherwise see'Functional Materials'6. semester bachelor

3.1 Biological materials



wood

shell

resilin

bone

silk

nacre

Mechanical materials: overall properties

Selected classification:

elasticity

strength

stiffness

hardness

plasticity

brittleness

rupture, fracture

toughness




Elasticity

low

extremelyhigh

wood

shell

resilin

bone

silk

nacre


Brittleness

high

zero low


elasticity

strength

stiffness

hardness

plasticity

brittleness

rupture, fracture

toughness




Plasticity

verylimited

wood

shell

resilin

bone

silk

nacre


Brittleness

high

zero low

verylimited

verylimited


elasticity

strength

flexibility

hardness

plasticity

brittleness

rupture, fracture

toughness




Plasticity

verylimited

wood

shell

resilin

bone

silk

nacre


elasticity

strength

stiffness

hardness

plasticity

brittleness

rupture, fracture

toughness


Brittleness

high

zero low

verylimited

verylimited

'contradiction' toclassical materials




Mechanical materials: functional aspects

pliant materials soggy 'soft' skeleton stiff materials

fibrous space‐filling mixture of proteins supportive, rigidmostly proteins mostly sugars and polysaccharides brittle properties

collagen polysaccharides, whole variety of very versatileamino acid chains proficient possibilities mechanical/viscoelastic due to large restricted linking in linking and branching, properties, gel, soft tissue, freedom in

cellulose, chitin (+water) cartilage composition

silk, resilin shell, nacrebone, wood




Mechanical materials: functional aspects

pliant materials soggy 'soft' skeleton stiff materials

fibrous space‐filling mixture of proteins supportive, rigidmostly proteins mostly sugars and polysaccharides brittle properties

collagen polysaccharides, whole variety of very versatileamino acid chains proficient possibilities mechanical/viscoelastic due to large restricted linking in linking and branching, properties, gel, soft tissue, freedom in

cellulose, chitin (+water) cartilage composition

mechanical properties and appropriate descriptions

Hook and non‐Hook viscoelastic propertiescomposite materials aspects

? fracture




Mechanics, revisiting what we thought to knowHook's law

macroscopic view microscopic view

εσ

εσ

εσ

d

dE =

∆∆

==

stiffness, Young's modulus

σ

ε

shear modulus

,...γτ

=G ( )υ+=

12

EG

short range forces between atoms

ν: Poisson's ratio

acf ∆= c: spring constant∆a: change in atomic distance

2

2

02

2 11

da

Ud

ad

UdE =

Ω=

ε




Mechanics, revisiting what we thought to knowHook's law and plasticity, which measure for strain and stress?

macroscopic view

0l

l∆=Cε ∆ℓ: change in length

ℓ0: initial length

true strain

ll /dd =ε concerns the actual true terms

)1ln( Ct εε +=

tε

σC,σt

σC

σt

εC

true stress σt, conventional strain εc

A0 ℓ0 = A ℓ A0/A = ℓ/ ℓ0 = 1+εC

σt = F/A = F/A0•A0/A = σC(1+εC)

plastic flow: volume is constant!

Ultimate tensile strength, conventional

0=C

C

d

d

εσ

i.e. horizontal tangent

more precisely: Considère criterion

The total load F is always

At the instability/necking point:




ttAF σ=

tttt dAdAdF σσ +== 0with volume constancy:

0)( =+== lll dAdAAddV ttt

with

ttt ddAdA ε−=−= ll //

tt

t

d

d σεσ

= )1ln( Ct dd εε +=and with

C

t

C

t

d

d

εσ

εσ

+=

1

εC

σt

Mechanics, revisiting what we thought to knowHook's law and plasticity, ultimate tensile strength

tt

t

t

t dA

dAd εσσ

=−=




Mechanics, revisiting what we thought to knowNon‐Hookean behavior, in view of ultimate tensile strength

σC

εC

])1(1[ 2−+−+= CCC const εεσstrain stiffening

linear, non-linear elastic

J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012





σC

εC




Stress-strain curve for amorphous plastic

rather low cross-linking

www.kazuli.com/UW/4A/ME534/lexan2.htm download 3-12-2013





σC

εC

σt

εC J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012

Considère

striking difference between conventional andbiological materials in necking and fracture!







σC

εC

σt

εC

For clarity


rubber or similar bio‐fibres


-1 0 1 2 3 4

σt

εC





σC

εC

σt

εC

For clarity


fibrous soft tissue, e.g.collagen containing biomaterial


-1 0 1 2 3 4

σt

εC





σC

εC

in consequence:'... nearly all biological materials have a concave stress‐strain curve .... there will belittle possibility of local increases in stress ...

σt

εC J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012

Polyethylen sample with a stable neckhttp://en.wikipedia.org/wiki/File:Stable_neck_MDPE.jpgdownload 8. July 2012


E

E u

E r

ωτ




Mechanics, revisiting what we thought to knowViscosity aspectssee Bachelor course'Structural Materials'

elastisch

elastisch

σe = E2 ε2

σv = 3ηε2

σe = E1 ε1

viskos

σ, ε

σ, εZener model

τ = τ * Er / Eu = const3ηE2

t

σ

σ1

t

ε

σ1Erσ1

Eu

Eu = E1

Er =E1E2

E1 + E2

10 ∞

⎭⎬⎫

⎩⎨⎧

⎟⎠⎞

⎜⎝⎛ −

=⎟⎠⎞

⎜⎝⎛ −

=τ

σστ

εε ttexp exp 00

actE/ητ =

unrelaxed modulus

relaxed modulus

EuEr

σ1

σ

ε

Eu

E

E u

E r

ωτ




Mechanics, revisiting what we thought to knowViscosity aspectssee Bachelor course'Structural Materials'

elastisch

elastisch

σe = E2 ε2

σv = 3ηε2

σe = E1 ε1

viskos

σ, ε

σ, εZener model

τ = τ * Er / Eu = const3ηE2

t

σ

σ1

t

ε

σ1Erσ1

Eu

Eu = E1

Er =E1E2

E1 + E2

10 ∞

⎭⎬⎫

⎩⎨⎧

⎟⎠⎞

⎜⎝⎛ −

=⎟⎠⎞

⎜⎝⎛ −

=τ

σστ

εε ttexp exp 00

actE/ητ =

unrelaxed modulus

relaxed modulus

EuEr

σ1

σ

ε

Eu

time dependent elasticity modulusor relaxation modulus




Mechanics, revisiting what we thought to knowViscosity aspects: time

classification of deformation properties

σC

time dependent

loading σC=constunloaded

unidirectional

time dependentrelaxation modulus

‐H(t)

relaxation spectrum function‐H(τ): negative derivative ofrelaxation modulus

analysis of polymer properties in terms of relaxation times




Mechanics, revisiting what we thought to knowYield and fracture

damping and viscosity, summary

Under construction

retardation spectrum (creep) relaxation spectrum (relaxation)

ε

εC

εt

rubber, isotropic and constant volume




Mechanics, revisiting what we thought to knowPoisson's ratio: an extended view

Definition:

Anisotropic material (biomaterials: up to 6 Poisson's ratios)

0.5 ≥ ν ≥ 0 from crystalline materials

cork, almost incompressible

∼ rubber, constant volume

however, biomaterials behavefrequently very differently

x

y

εε

ν −= -σσxε

yε

skin from cow's teat

σ





-σ

probably cow's teat

after: J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012

belly skin

very smallin very anisotropic case:locust intersegmental membrane cuticle

Unusual, 'strange' Poisson ratios

≥ 0.5 generally indicative of

• trelliswork structures(two‐ dimensional)

•Open feltwork structure(three‐dimensional)

'strange' Poisson's ratios

• network with special fixed knotsstrut frameworkuniquely oriented 'hinged bonds'(auxetic material)

Unusual Poisson ratios

≥ 0.5 generally indicative of

• trelliswork structures(two‐ dimensional)

•Open feltwork structure(three‐dimensional)

very small

•in very anisotropic case:locust intersegmental membrane cuticle

'strange' Poisson's ratios

• network with special fixed knotsstrut framework





σ

-σprobably cow's teat

after: J. Vincent, Structural Biomaterials, Princeton University Press,1982,1990,2012

belly skin

Unusual Poisson's ratios in fibrous networks, very anisotropic, with spatially fixed knots even negative ones!

Question:Is Poisson's ratio generally the suitable term to characterize themechanical property of a bio‐material?

What would be an alternative?




Protein‐based elements

Protein: polymer made of amino acids, either fibrous or space fillingmechanical properties determined by the amino acid sequence and side groups

electron cloud around peptide ring holding theamide group in a single plane

restricted rotation around backbone, cf. polysaccharides

basic structure of amino acid

R: radical, see next slideα: central C-atom is α-atom

Polymerization

bond dimensions [nm] and angles





Protein: polymer made of amino acids, either fibrous or space fillingmechanical properties determined by the amino acid sequence and side groups

Classification: primary structuressecondarytertiaryquaternary

Structural proteins:keratinssilkscollagenselastins

Summary




R: radical, side groupα: central C-atom is α-atom

Polymerizationbasic structure of amino acid

double bond oscillateskeeps structure in planeno rotation

amide linkpeptide bond

φ, ψ: dihedral anglespermitting rotations





electron cloud around peptide ring holding theamide group in a single plane

restricted rotation around backbone, cf. polysaccharides(later) moredegrees of freedom

spatial basic structure of amino acid

Polymerization

bond dimensions [nm] and angles

C‐O N‐H

Vincent 1st ed.





Protein‐based elements: reason for self organized conformationprimary structure: α‐helix and β‐sheet

N‐H ‐‐‐‐ O hydrogen bridge

only when wound into a helix(α‐helix ) orplaced parallel to each other(β‐sheet)




Protein‐based elements: sterical structure α‐helix

Die α‐Helix ist eine 3,613 Helix. 3,6 Aminosäuren in einer Windung (360°). Die sich ausbildende H‐Brücke bildet einen 13‐gliederigen Ring.

N‐C‐Cα‐N

helix axis

O

H

5.4 Å

view along helix axis

http://www.cup.uni‐muenchen.de/oc/carell/teaching/Bioorganik/B1allgemeines.pdf

radicals almostperpendicular tohelix axis




Protein‐based elements: sterical structure α‐helix

Die α‐Helix ist eine 3,613 Helix. 3,6 Aminosäuren in einer Windung (360°). Die sich ausbildende H‐Brücke bildet einen 13‐gliederigen Ring.

N‐C‐Cα‐N

helix axis

O

H

5.4 Å

view along helix axis


radicals almostperpendicular tohelix axis

There is a steric problemfor helix formation:

side chains can be very largeand hinder helix formation stericallyor by other interactions with mainstring




conformation (self‐organized spatial structure):

side group's chemical nature –acidic, basic, polar, neutral‐determines self‐interaction back bone and side groups

amongst themselves and with each other.

for three letter‐coding of amino acids see annex

Protein‐based elements: typical side groups and broad properties



3.1 Biological materials Vincent 3rd ed.

Protein‐based elements: typical side groups and broad properties

importantExample:

1 glycile residue: no side chainonly R=H, no favorable factor+ CH2

2 alanine, interactions favorablefor helix formation+ C‐ONH2

3 asparagine, this polar side chaininteracts electrostatically withpeptide group and destabilizes helix+ extra CH2

4 glutamine, restores helix, probably because charges aretoo far apart

12

34

http://en.wikipedia.org/wiki/File:TRNA_all2.png

secondary structure

tertiary structure

http://en.wikipedia.org/wiki/File:Protein_structure.png




Protein‐based elements: sterical structure β sheet


parallelH‐bonds strained,

higher energy state than

antiparallel(folded) β sheet

H‐bonds not strained




hierarchical structure

Structural proteins: keratin (α‐keratin)

mostly in vertebrats ashorn, hair, hoof, feather, skin

different keratin types:

mammalian, avian, reptilian

cross‐linking based on

sulfur or tyrosine,these break the helix!

amorphous regionsand oriented helices

bimodal material

rope‐like super structuresembedded in non‐fibrousmatrix like two‐phase material

wool relative humidity

same initial modulus

H‐bonds rupture and destabilize helicestowards β‐sheet fromation

final high modulus:contribution of back‐bone

Hair. wool:




hierarchical structure

Structural proteins: keratin (α‐keratin)

rope‐like super structuresembedded in non‐fibrousmatrix like two‐phase material

Horn (rhinozeros)

mechanical anisotropy

very large mechanical hysteresis inhairreturn curve: helices reform

high toughness: most energyexpended for deformation is notstored and thus not availablefor fracture

covalent




Structural proteins: silkfrom Bombyx mori (silk‐worm)

β‐sheet antiparallel, large part of fibre

high strength in fibre axis, backbone stretchingin‐plane H‐bondings perpendicular to backbone

ensure planar structurevan der Waals bonding permits flexibilityH‐ and v.d.Waals‐bonds transmit shear forces

a: alanine (R= H)g: glycine (R= N)

role of side groups:the more bulky the less ductile

fig 2.17




Structural proteins: collagen

Most common fibregenerally in tissues,muscles (tendons)winding of pressure vessels

basis for glues and gelatins

single fibre: three 'slow' left‐handedhelices, hydrogen‐bonded




Structural proteins: brief summary for fibres with preferential bonds along themolecule and fibre dominated compounds

• reasonably large range of elasticity, depends on side chains• very high elasticity moduli after a varying range of low modulus deformation• i.e. relatively high modulus and restricted extensibility• extremely anisotropic mechanical properties• regular sequence of amino acids determines the conformation, mostly helices,

by formation of hydrogen bonds and/or v.d.Waals bonds• expression of conformation reduced by water due to bond weakening

depending on structure/conformation, compounds can be very rigidand carry large tensional forces and/or

show high or low damping capabilitiesmaterials are extensible essentially due to amorphous regions in compounds




Structural proteins: highly extensible fibres, 'protein rubbers

Elastin: very low elastic modulus and high extensibility, reduced viscoelastic character,Reason again: structure determines conformation

http://www.kopfgelenke.de/7‐bandstrukturen‐der‐halswirbelsaule/2008/12/07/download 13.7.2012

ligamentum nuchae80%, remainder collagen

E∼0,6 MPa

E∼35 MPa




Structural proteins: highly extensible fibres, 'protein rubbers

Elastin: very low elastic modulus and high extensibility, reduced viscoelastic character,Reason: again structure and conformation


ligamentum nuchae

E∼0,6 MPa

E∼30 MPa

β‐turn of elastin with possible rotationsthat cause high elasticity, supported by0,4 % covalently cross‐linking amino acidsVal: valine (helix former)Gly: glycinePro: proline




Structural proteins: highly extensible fibres, 'protein rubbers'

Elastin: very low elastic modulus and high extensibility, reduced viscoelastic character,Reason again: structure determines conformation


elastin double fibredimensions in nm

helix breakerβ‐turns in primary helix



Structural proteins: highly extensible fibres, 'protein rubbers'

Elastin: very low elastic modulus and high extensibility, reduced viscoelastic character,Resilin, Abductin: even higher elasticity because of higher content of helix breakers


up to 87 %64 %45 %helix breakers

abductinresilinelastin

brief summary 'protein rubbers'

• Very high extensibility at rather low elastic modulus• work best with water as plastiziser• Differences in properties due to changes in composition:

elastin: mostly for static tensile loading (head of cow,horse)resilin: mechanical energy storer in insects, flight mechanism, slow storing of

energy and fast release at start of wing stroke, or locust/flee jump• very small energy loss, 'resilience' R=1‐2πtanδ (1‐energy loss in hysteresis loop)

R(resilin) 96‐97%, avoids overheating in flying animal• abductin: properties in between, resilience lower (80 %)

β

variations in molecularsteric configuration(side view):2 boat2 chair

6

4

5 2

3 1




Sugars and polysaccharides

Basic elements: hexoses

position 6: various side chains(residues)

Haworth formula

steric configurationand nomenclature forthe C‐atoms

α

D: dextro rotary

Definitions

1

1





Polymerization

β 1‐4 linkage, large freedom of rotation around Φ and Ψ

+H2O

low energy configuration due toH‐bond formation by appropriate rotation

Cellobiose formation Haworth formula





Polymerization

β 1‐4 linkage, large freedom of rotation around Φ and Ψ

+H2O

low energy configuration due toH‐bond formation by appropriate rotation

Cellobiose formation Haworth formula

Many more linkage possibilities

Each H is a possible siteEach monomere: 5 docking sitesbecause of α and β conformation10 possibilities

100 possibilities for a disaccharideEven more possibilities because of3 bonds at a C‐atom bound to position 5




Further characteristics of saccharides (compare to proteins)

1. Less variety of side chain types with respect to size, conformation, polarity/charge.

But: No hydrophobic interactions, i.e. hydration, hydrogen bonding, or ionic interactions

2. Large variety of bonding between polysaccharide residues (compared to proteins)

Thus much greater variety of periodic structures (as compared to proteins)

Over long saccharide chains, attractive forces between (complementary) chainsmay become dominant leading to extremely stable types of biomaterial:

fibers, elastic gels (e.g. carrageenan) and viscoelastic gels (e.g. hyaloronic acid)




Three main types of pure polysaccharides: fibre, elastic gels, viscoelastic gelsinterconvertible

Fibresback bone elasticity with strong shear contributions by intermolecular H‐bonds

Cellulose

Chitin

spatial arrangement next






‐‐‐‐ hydrogen bonds back bone direction

cross direction in plane cross direction in plane

α‐chitin

sheet normal






Consequences of these types of conformation

1. high modulus, up to more than 100 GPa, aided by the many H‐bonds2. reduced degree of crystallinity (i.e. higher amorphous part) reduces

this modulus3. removal (inactivation) of H‐bonds (water!) reduces modulus by up to factor 44 Chitin much stiffer than cellulose,because the acetylic side chainsoffer more H‐bonds and strong steric hindrances





Gelspolysaccharides with alternating 1,3 and 1,4 links

example

β 1‐3 link





Gelspolysaccharides with alternating 1,3 and 1,4 links

example

1. form extended helices, intertwinedor nestled with each other

2. very stable structures in water,3. water trapped in various ways: sugar

units carry negative charges, drives the chains to an extended conformation, entrains large amounts of water, strongly(double H‐) and weakly (single H‐) bond water, trapped in compartementsformed by structure (mixture also entropically driven).

5. typical solid content of elastic gel: 2 %6. charges cause strong effects on added ions





Ions like Ca2+, Na+,K+, Mg2+, can beincorporated here

••

•

•

•

see Anderson, J. Molecular Biology 1969





Gels: some properties

10‐s compliance of2% alginate gel inwater, pH 6.0 as afunction of Ca2+‐citrate. Ca causes rigidity

10‐s compliance ofalginate gel in water,pH 6.0, as a functionof alginate content.compliance increaseswith alginateconcentration

compliance = ε/σ





Shear stiffness (modulus)of pedal mucus (AriolimaxColumbianus) as a functionof water content.Lubrication by water veryefficient at >80 % water

mind log and scale

Gels in plants are mostly extracellularthat maintain plant's osmotic environment,give physical protection and controltransport of metabolites

Gels: some properties

property: brittle plasticH2O binding: high small

Stress‐strain curves of aragose, κ‐ and λ‐ carrageenan as 2% gels. Thedifferences in extensibility are due tothe degree of binding of the water.

Vincent 3rd ed.





Fig 3.16in animals

Hyaluronic acid family of animal polysaccharides

polyuronides orglycosaminoglycansassociated with proteins





Fig 3.16in animals

Hyaluronic acid family of animal polysaccharidesMolecular weight: 106 – 107 or even moreMolecule length: 2.4 m, occupies in liquid

a sphere with 1 m diameter!

Consequence: 1 g hyaluronic acid occupies 5 l.High binding capacity of water, extensive spanof mechanical properties from large stiffness(dry state), over decades of viscosity to highplasticity and liquid viscosity





Fig 3.18

Real (G') (shear) modulus and imaginary (G'') (loss) modulusas a function of frequency.Hyaluronic acid. ω: oscillation frequencyThe elastic field (G') takes over at/towards larger frequencies,here around 1 kHz, i.e. essentially elastic instead of viscous behavior

Viscocity decreases withshear rate drastically

This property is relevant to lubrication,e.g in knee joints. Slow motion: elastic,fast motion: material is almostliquid and serves as lubricant.Reversible.

Hyaluronic acid family of animal polysaccharides

(η=G''/ω)

http://de.wikipedia.org/wiki/Ariolimax_columbianus


Sugars and polysaccharides,

Hyaluronic acid family of animal polysaccharides, mucus with similar, yet much enhanced properties


Pedal mucus from slug Ariolimax columbianus= 'banana slug'


Denny 1981





Pedal mucus from slug Ariolimax columbianus= 'banana slug' : saccharide plus certain amount of

protein, 'strange material' (Vincent)


viscoelastic properties ofmucus pomatia

low rates of deformation and strain < 0.1:viscoelastic solid, a little flow only

at high shear rate: behaves like rubbery stuff,BUT: this gel strained to ∼5, ist network breaks down

fluidic behavior! once shear stops, solid rubbery again

fast con‐traction

wave, speed say 2v

F

fluidsolidsolid solidfluid

substrate no shear force

mucus

foot ofslug

fast con‐traction





Pedal mucus from slug Ariolimax columbianus= 'banana slug' : saccharide plus certain amount of

protein, 'strange material' (Vincent)


low deformation rates at strain < 0.1:viscoelastic solid, a little flow only

at high shear rate: strain ∼5, fluidic behavior

! shear stops, solid rubbery again

v velocity of slug

fixed

principle of slug's crawling

Note: crawling is of all existingmotional principles(swimming, flying, running)the most inefficient one

We keep in mind:

∼10 µm




Combination of protein and polysaccharide fibres (soggy materials)

Model of soft tissue ('bottle brush model')

(Collagen‐proteoglycan‐hyaluronic acid model, proteoglycan in bottlebrush conformation, binds large amounts of water!)

Cartilage consists of a gel as matrixand a distribution of protein fibres, that form a dense network at the surface.Stability and rigidity due to osmotic swellingby incoming waterthat puts proteins in tensional pre‐stress.

One example only for stabilization: cartilage (rigidity from water)

observed proteinorientations

model




stiff materials, fibrous composites

Remind: biological elements treated so far:

1. proteinsform fibers, layers and volume materialmechanically anisotropic behaviour, strongly governed by side chainselastic and viscoelastic properties in a wide range: frompurely elastic with high elastic modulus to highly damping

2. polysaccharidesform fibres, due to very many interactions very large spectrumof mechanical properties

esp. gel forming by water incorporation to very large percentages, and spectrum from elastic to stiff, velocity dependent

sensitive to pH and metal ions

3. Combinations: hard, elastic, viscous materials, easy‐to‐change between




stiff materials, fibrous composites

voigt-reuss Fig 5.5 Fig 5.1 Teil 4,5

Remind: important biological elements treated so far:

1. strong fibre structures: proteins2. variably strong matrix/volume structure: polysaccharides with water

Treatment of their composites with classical fibre strengthened materials

Key words: Elasticity: Voigt, ReussPlasticity: fibre reinforced materialsCracks: crack formation, crack blunting, crack deflection by microcracks

Voigt

Reuss

modulus

composition

equal strain

equal stress




net wood structure

evtl 5.27, 5.28

http://www.msm.cam.ac.uk/schools/Physics_Update_practicalsA.pdf

stiff materials, fibrous compositewood

Note: cotton is >99% cellulose

Lignin: binds structuretogether in cell and incell walls

Cellulose:

http://nsm1.nsm.iup.edu/jford/projects/Cellulose/Wood_McBroom.pdf

phenylpropane unit




net wood structure

evtl 5.27, 5.28


stiff materials, fibrous compositewood primary wall

secondary wall

middle lamella

inner layer S1, 50‐70°



fibre angleswith long axis

Tracheid fractured in tension,

S2 layer, dissection betweenhelically wound cellulosefibres

20 µm




fibre angleswith long axis




net wood structure

evtl 5.27, 5.28


stiff materials, fibrous compositewood primary wall

secondary wall

middle lamella

inner layer S1

inner layer S2

inner layer S3

fracture surfaces(deformed in tension)

left: cross fracturedS2 tracheid layers

right: fracture alongS2 tracheid layers

top: fractured S2 tracheidlayer to show thelayered stack type

10 µm

50 µm




stiff materials, compositesBiological Ceramics

Protein skeletons (eg. chitin) have to be synthesized

expensive

ceramic material is strongbut generally brittle

cells build compositesby tayloring crystalline andorganic material

3.1 Biological materials:


3.2 Biomimetic materials

stiff materials, compositesmollusc shells

extract from table 2

30/40 150/200 40/60very tenuous0,1‐0,3%

Clong thin crystalsin overlappinglayers

foliated

30 250 60very tenuousAfine scale rubble 0,5‐3,0 µm diam

homo‐geneous

40/60 250/340 60/80very tenuous0.01‐4%

Aplywood‐like 20‐40 µm thick

crossedlamellar

130 380/420 60 :wet

167 70 :dry

thin layer in between 1‐4%

Aflat tablets 0.3‐0.5 µm thick

nacreous

MPa MPa GPa

60/60 250/300 30/40

5 µm sheetaround eachprism 1‐4%

C calcitearago‐

nite A

polygonal columns0.1‐0.2 mmdiam.

several mm long

prismatic

mechanical strength, average/max, tension/compression/Young

protein matrix, wt‐%

ceramicmaterial

shapemollusc

shell type

C calcite, aragonite A




stiff materials, composites

100 µm

5 µm

sheets flat tablets(0,3‐0,5µm) of aragonite, thinprotein layerin between

prismatic shell material Nacre

fracture pathviewed in orientation A

Elastic and fracture properties strongly anisotropic




schematic structuresingle rod like crystals betweenadjacent ends of collagen fibrescrystals form 'epitaxially'

stiff materials, compositesbone

100 µm




schematic structuresingle rod like crystals betweenadjacent ends of collagen fibres,crystals might form 'epitaxially'

stiff materials, compositesbone approaches to describe bone as a composite




stiff materials, compositestooth

human incisor

3.2 Biomimetic materials:


3.2 Biomimetic materials

artifical materials purposely producednacre

Bill Arbeiten

3.3 Biological concepts


3.3 Biological concepts

preparation of artifical materials to imitate properties optimized by nature





Amino acids

+ Selenocystein and Pyrrolysinthat become coded






Amino acidsone and threeletter codes



Made of basic elementsof hexoses:





Made of basic elementsof hexoses:







Mechanics, revisiting what we thought to knowViscosity aspects

role of water hydrophobic/-philic behavior p. 28

C

CCt

d

dd

ddd

εεεε

+=

+===

10

00

0 ll

l

l

l

l

l

l

l




Plasticity

verylimited

wood

shell

resilin

bone

silk

nacre


elasticity

strength

stiffness

hardness

plasticity

brittleness

rupture, fracture

toughness


Brittleness

high

zero low

verylimited

verylimited

contradiction toclassical materials




Elasticity

low

extremelyhigh

wood

shell

resilin

bone

silk

nacre


elasticity

brittleness

strength

hardness

toughness

flexibility

plasticity

rupture, fracture





Mechanics, revisiting what we thought to knowYield and fracture

advanced materials and material characterization€¦ · · 2014-08-05advanced materials and...

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