Abstract

Holey Material Properties! Multiscale Modelling of Effective Properties of a Bulk Substance Containing Pores and Particles

Louise Wright, Neil McCartney, and John Blackburn: National Physical Laboratory, UK

Davin Lunz: Centre for Doctoral Training in Industrially Focussed Maths & Modelling, Oxford University, UK

Many materials feature small inclusions or voids. Some inclusions, such as particle reinforcements, are introduced deliberately to enhance a desirable property of the material. Some inclusions are undesirable by-products of the manufacturing process, an important example being the porosity and dust inclusions that occur in some additive manufacturing processes. Some inclusions develop whilst a material is in service, for example due to chemical or thermal degradation. 

In all cases, the effective properties of the material (bulk substance and inclusions) determine the behaviour of the material and are key to assessing product performance and lifetime. Understanding how the shape, size and distribution of the inclusions affect the effective properties can allow materials to be designed to achieve required performance and minimum cost, and support development of measurement and characterisation standards for such materials. Continuum multiscale modelling methods enable the effective properties of such materials to be derived based on a consideration of the small-scale detail of the bulk material and its inclusions. Methods range from compact analytical methods [1,2] to more complicated but less restrictive numerical techniques [3,4].

This talk will describe work that has been carried out using multi-scale models for effective property calculation at the National Physical Laboratory. We will give an overview of possible approaches and their limitations, discuss how the relevant inputs for the models can be obtained, and will illustrate the importance of the use of appropriate material properties using an example of a material that undergoes degradation during service. 

References

[1] L. N. McCartney and A. Kelly. “Maxwell’s far-field methodology applied to the prediction of properties of multi-phase isotropic particulate composites.”, 28, Proc. R. Soc. A, 2008.

[2] L.N. McCartney. “Maxwell’s far-field methodology predicting elastic properties of multiphase composites reinforced with aligned transversely isotropic spheroids.” Philosophical Magazine, 90 (31-32), 4175–4207, 2010.

[3] Sanchez-Palencia E. “Solutions périodiques par rapport aux variables d’espaces et applications.” C R Acad Sci Paris, Sér A–B, 271:A1129–32, 1970.

[4] Gareth Wyn Jones. “Static Elastic Properties of Composite Materials Containing Microspheres.” PhD thesis, Jesus College, University of Oxford. Michaelmas 2007.

About the Speaker

Louise Wright, National Physical Laboratory 

Originally trained as a mathematician, Louise Wright has worked with finite element analysis for over 20 years. Her first two jobs involved simulating vehicle impacts and roof tile production processes, before she joined the National Physical Laboratory in 1999. Since joining NPL she has used FE and related numerical techniques to solve problems across application areas from acoustics to electromagnetics and heat transfer to hydrogen embrittlement. Her current interests include multi-scale modelling to support prediction of bulk-scale behaviour for crystalline materials and composites, by combining measurements of component properties and imaging of microstructure.