Experimental and numerical characterisation of in-plane deformation in two-phase materials q E. Soppa a, * , P. Doumalin b , P. Binkele a , T. Wiesendanger a , M. Bornert b , S. Schmauder a a Staatliche Materialpr ufungsanstalt, Universit at Stuttgart, Pfaenwaldring 32, 70569 Stuttgart, Germany b Laboratoire de M ecanique des Solides,  Ecole Polytechnique, 91128 Palaiseau cedex, France Abstract The aim of the present work consists in the comparison of in-plane strain ®elds with out-of-plane displacements in micro-areas of an Ag/Ni-composite after a macroscopic compressive deformation of 8.6%. The in-plane deformations in an Ag/Ni-composite have been analysed experimentally with a high resolution object grating technique and nu- merically using the ®nite element method. The out-of-plane displacements were measured with an atomic force mi- croscope AFM). The development of local strain ®elds in micro-areas at the surface of an Ag/Ni-composite was simulated numerically using the FE-method in plane strain condition. A real cut-out of the microstructure served as input for the calculation. The out-of-plane displacements determined by AFM measurements were used further to correct the in-plane values of strains evaluated by the object grating technique. The roughness on the surface of the sample was characterised by fractal dimensions and compared with the in-plane strains in the same micro-re- gion. Ó 2001 Elsevier Science B.V. All rights reserved. Keywords: Microstructure; Computer simulation; Whole ®eld measurement of strain; AFM measurements; Fractal dimension 1. Introduction Stress and strain distribution in two-phase ma- terials under loading is inhomogeneous. The magnitude of the inhomogeneity as well as local strain patterns depend on the microstructure i.e. the elastic±plastic behaviour, volume fraction and phase arrangement of the components). The knowledge of the microstructure/deformation-re- lationship enables ``tailoring'' of materials with desired pro®les of properties. The critical concen- tration of strain, stress or hydrostatic stress can lead to damage initiation and failure of the com- ponent. By an optimised microstructure design such stress and strain concentrators can be avoi- ded or reduced. 2. Material and microstructure The subject of the following experimental and numerical investigations is a model material Ag/ Ni57%)-particulate composite with a coarse microstructure with an average Ni-phase size of www.elsevier.com/locate/commatsci Computational Materials Science 21 2001) 261±275 q Paper contributed to Ninth International Workshop on Computational Mechanics of Materials, J. Olschewski, S. Schmauder Eds.), BAM, Berlin, Germany, October 4±5, 1999, Comp. Mater. Sci. 19 2000). * Corresponding author. Tel.: +49-7-11685-2579; fax: +49-7- 11685-2635. E-mailaddress: ewa.soppa@mpa.uni-stuttgart.de E. Soppa). 0927-0256/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0927-025601)00170-7