tailieunhanh - Generalized continuum overall modelling of periodic composite structures

The overall substitution medium is shown to provide improved predictions compared to standard homogenization. In particular the additional boundary conditions required by generalized continua makes it possible to better represent the clamping conditions on the real structure. | Vietnam Journal of Mechanics, VAST, Vol. 33, No. 4 (2011), pp. 245 – 258 GENERALIZED CONTINUUM OVERALL MODELLING OF PERIODIC COMPOSITE STRUCTURES Duy Khanh Trinh, Samuel Forest MINES ParisTech Centre des matériaux, CNRS UMR 7633 BP 87, F-91003 Evry Cedex, France Abstract. Classical homogenization methods fail to reproduce the overall response of composite structures when macroscopic strain gradients become significant. Generalized continuum models like Cosserat, strain gradient and micromorphic media, can be used to enhance the overall description of heterogeneous materials when the hypothesis of scale separation is not fulfilled. We show in the present work how the higher order elasticity moduli can be identified from suitable loading conditions applied to the unit cell of a periodic composite. The obtained homogeneous substitution generalized continuum is used then to predict the response of a composite structure subjected to various loading conditions. Reference finite element computations are performed on the structure taking all the heterogeneities into account. The overall substitution medium is shown to provide improved predictions compared to standard homogenization. In particular the additional boundary conditions required by generalized continua makes it possible to better represent the clamping conditions on the real structure. Keywords: Homogenization, strain gradient effects, periodic micro-structures, numerical prediction. 1. INTRODUCTION Computational analysis of composite structures is based on the consideration of homogeneous effective behaviour of the heterogeneous material. Such effective properties can be deduced from the knowledge of the detailed arrangement of the constituents by means of homogenization methods, as depicted in [24]. Classical homogenization methods root on the assumption of separation of scales, meaning that the size of the heterogeneities must be significantly smaller than the minimal structure size, or, more precisely, .