
Modelling materials
with negative Poisson's ratios
Materials with a negative Poisson's ratios (auxetic)
exhibit the very unusual and intersting property of becoming wider when
stretched and thinner when compressed. My research entails the modelling
and simulation of the mechanical properties of materials in an attempt
to discover or design materials with this unusual property. Several new
auxetic nano/micro/macrostructures have been invented and explored in detail.
Particularly interesting results include the discovery
of negative Poisson’s ratios in the zeolite class of materials, the design
of various networked polymeric auxetics and, the development of models
for predicting the mechanical properties of auxetic foams and of microporous
polymers. Some of these discoveries have a number of very important technical
implications (e.g. the discovery of negative Poisson’s ratios in zeolites
which opens many new possibilities towards the use of zeolites as tunable
filters).
Recent
publications:
(a) Printed publications:

J.N. Grima and K.E. Evans, Rotating squares with negative
Poisson's ratios, J. Mat. Sci. Lett., 19 (2000) p.15631565.

J.N. Grima and K.E. Evans, Self expanding networks,
Chem.
Comm., (2000) p.15311532.

C.W. Smith, J.N. Grima and K.E. Evans, A novel mechanism for
generating auxetic behaviour in reticulated foams: Missing rib foam model.Acta
Materiala, 48 (2000) p43494356.

J.N. Grima, R. Jackson, A. Anderson, K.E. Evans, Do zeolites
have negative Poisson's ratios? Adv. Mater., 12 (2000)
p. 19121918..

C.W. Smith, J.N. Grima, B.D. Caddock, R.J. Wootton and K.E. Evans,
Microstructures
producing negative Poisson's ratios: Experiment and models, SEM
Theoretical, Experimental and Computational Mechanics Preprints (1999)
p.184187.

J.N Grima and K.E. Evans, Networked polymers with negative
Poisson's ratios, ACS Polymeric Materials Science & Engineering
Preprints, 83 (2000) p. 367368.
(1) Reviewed by the Philadelphia section of the
Society of Plasitcs Engineers, USA, in Philadelphia Plastics Press, Nov.
2000  "... this paper describes how an arrangement of squares can lead
to auxetic behaviour. ... I expect to see several new patents from the
Philadelphia Section members two to ten years from now because of this
important revelation."
(2) Selected as Hot Paper by editors of Chemical Communications
(b) Papers presented at international conferences:

J.N Grima and K.E. Evans, The modelling and synthesis of auxetic
materials, Paper presented at the 3rd Materials Chemistry conference,
Exeter (UK), July 1997 (P125).

C.W. Smith, J.N. Grima, L.G. Bridger, B.D. Caddock, R.J. Wootton
and K.E. Evans, Microstructures producing negative Poisson's ratios:
Experiment and models, Paper presented at the Spring Conference
of the Society for Experimental Mechanics, Cincinnati (USA), June
1999.

J.N Grima and K.E. Evans, Molecular auxetic materials,
Paper presented at the 4th Materials Chemistry conference, Dublin (Ireland),
July 1999 (B2.1).

J.N Grima, A. Alderson and K.E. Evans, Zeolites with negative
Poisson's ratios, Paper presented at the 4th Materials Chemistry
conference, Dublin (Ireland), July 1999 (P81).

J.N. Grima and K.E. Evans, Networked nanostructured polymers
with negative Poisson's ratios, Paper accepted for publication
at the Materials Research Society Spring Conference, San Francisco (USA),
April 2000.

J.N. Grima, A. Alderson and K.E. Evans, Zeolites with negative
Poisson's ratios, Paper presented at 220th ACS National Meeting
(Inorganic Division), Washington DC, August 2000.

J.N Grima and K.E. Evans, Networked polymers with negative
Poisson's ratios, Paper presented at 220th ACS National Meeting
(PMSE Division), Washington DC, August 2000.

J.N. Grima, A. Alderson and K.E. Evans, Modelling zeolites
with negative Poisson's ratios, Paper presented at 2nd Inorganic
Materials Conference, Sta. Barbara, USA, September 2000.

A. Alderson, J. Rasburn, J.N. Grima and K.E. Evans, Auxetic
polymeric filters: Tunable filters displaying enhanced defouling and pressurecompensation
properties. Paper accepted for publication at the Polymer '01 conference,
Bath, UK, March 2001.
(c) Others:

J.N Grima, Auxetic behaviour through rotating triangles,
SOE Departmental Seminar, University of Exeter, UK. September 1998.

J.N Grima, Negative Poisson's ratios at the molecular level,
Materials Research Group Seminar, University of Exeter, UK. July 1999.

J.N. Grima, New Auxetic Materials  Vols. 1 & 2,
Ph.D. Thesis, University of Exeter, UK. March 2000.
