concepts for novel materials and added functionality · pdf fileyoung’s modulus (fibre...
TRANSCRIPT
NATURAL CELLULOSE-BASED HIERARCHIES:
CONCEPTS FOR NOVEL MATERIALS AND ADDED FUNCTIONALITY
George JeronimidisCentre for BiomimeticsReading University
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
• Cellulose fibres from plants
• Advantages and limitations of cellulose fibres/nanofibres
• Cellulose fibres/nanofibres as reinforcement in composites
• Benefits of hierarchical structures
• Conclusions
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
www.susalrugs.co.uk
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
D. Robson et al. (1993)
images-mediawiki-sites.thefullwiki.org
C. Parker, 2002
Sources of cellulose fibres and nanofibres
www.cheme.cornell.edu
Scale bar: 3μm
+ Bacterial Cellulose
Young’s modulus (fibre direction) 134 GPaTensile strength 7.5 GPaDensity 1500 kg/m3
Nanofibre diameter 50 ~ 200 nm [Frone et al., 2011]Nanofibre aspect ratio (L/d) 10 ~ 30 [Eichorn et al., 2010]
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Typical properties of cellulose nanofibres
www.cheme.cornell.edu
Scale bar: 3μm Frone et al., 2011Borges et al., 2008
Young’s modulus (fibre direction) 134 GPaTensile strength 7.5 GPaDensity 1500 kg/m3
Nanofibre diameter 50 ~ 200 nm [Frone et al., 2011]Nanofibre aspect ratio (L/d) 10 ~ 30 [Eichorn et al., 2010]
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Typical properties of cellulose nanofibres
HOW CAN THESE PROPERTIES BE EXPLOITED EFFECTIVELY ????
www.cheme.cornell.edu
Scale bar: 3μm Frone et al., 2011Borges et al., 2008
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Advantages of cellulose nanofibres (CNF)
High modulus and high specific modulus[compares well with glass, aramid an carbon]
High tensile strength[theoretical strength of solids is of the order of E/10, CNF has a value of E/18]
Limitations of cellulose nanofibres
length diameter aspect ratio (L/d)
surface chemistry (compatibility with polymer matrix systems for composites)
loss of hierarchical organisation and limited control of fibre orientation (benefits of cell wall structure/density)
limited compressive strength because of fibre buckling
Eichorn et al., 2010
Composite modulus for a unidirectional fibre composite as a function of cellulose nanofibre aspect ratio at a volume fraction of fibres of 50% (PP matrix)
= continuous
c
cf
yi E
EdLσ
τ
Length-diameter aspect ratio
d = diameter
yτ = matrix shear strength
Ef = fibre modulusEc = composite modulus
σc= composite tensile strength
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
2121 41
81
85
83 :1968 (2D), Model Pgano-Tsai
41
8
6 :1952 (3D), ModelCox
31
8
3 :1952 (2D), ModelCox
EEGEEE
vEG
vEE
vEG
vEE
ffff
ffff
+=+=
===
===
ν
ν
E1, E2, G12 = Elastic and shear moduli of unidirectional discontinuous fibre composite
Fibre orientation
Ef = Fibre modulus
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Fibre orientation, volume fraction and fibre/matrix modulus ratio
Dependence of Normalised Composite Modulus (random fibres) on fibre/matrix modulus ratio and fibre volume fraction.
E1 is the Young’s modulus of a continuous unidirectional fibre composite in the fibre direction
Hugues (1979)
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Fibre buckling in plant cell walls
Benefits from hierarchical structures
• Compensation for limitations of unidirectional composite• Cellular structures possible (low density) • Beneficial fibre pre-stressing in tension (buckling)• Control of swelling• Multiple energy absorption mechanisms against fracture• Modulation of multiple interfaces
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Layered composite structures
M. Bramwell, 1976
Hygro- or thermal expansion of angle-ply composite structures
Individual plies with non-zero coefficients of thermal expansioncan create a laminate structure with zero thermal expansion coefficient
Similar effects are possible with hygro-expansivity
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Halpin and Pagano, 1969
H. Lichtenegger et al., 2000
2Energy absorption failureEε∝
Dependence of Young’ s modulus and failure strainin wood as a function of microfibrillar angle in S2
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Boatright & Garrett, 1983
Jeronimidis, 1978
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Glass sponge Euplectella – hierarchical architecture
Layered structure as a defense against brittle fracture
Aizenberg et al., 2005; Weaver et al., 2007; Fratzl,2010
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Semi-ductile fracture of nacre in tension (95% brittle ceramic) resulting from hierarchical organisation and control of interfaces
A. Jackson and JFV Vincent, 1980
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Hierarchy of nacre
E.Baer, 1987
POLYMER MATERIAL IN TENSION
Transition from semi-brittle to ductile fracture induced by layered hierarchies
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Bolton & J.A. Petty, 1975
Jeronimidis, 1978
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
Preventing fracture from bordred pits via modulation of fibre orientation
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
GROWTH AND HIERARCHICAL STRUCTURES
(a), (b) J.R. Barnett (pers. comm.); (c) J.M. Dinwoodie, 1979
(a)
(b)
(c)
Giddings et al., 1980
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
The role of microtubules for cellulose fibre organisation in cell walls
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
We cannot replicate growth and all its associated control, sensing andmodulation mechanisms which lead to successful biological hierarchical structures
However, we can extract principles of good composite design from biological systems which are continuously adapting and compromising
Introducing levels of hierarchy can provide better utilisation of fibres and achieve higher levels of functionality
CONCLUSIONS
“MATERIAL” LEVEL
Fibres, Matrices, Anisotropy, Heterogeneity
FUNCTIONAL INTEGRATION AT THE “SYSTEM” LEVEL
+“STRUCTURE” LEVEL
Hierarchies, Dimensions, Geometry, Shape
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA
THANK YOU FOR YOUR ATTENTION
THE UNIVERSITY OF READING – CENTRE FOR BIOMIMETICS IAWS 2011 - INNVENTIA