Comput.Model.Engng.Sci. 5, 5-20, 2004

MULTI-INCLUSION UNIT CELL STUDIES OF REINFORCEMENT STRESSES AND PARTICLE FAILURE IN DISCONTINUOUSLY REINFORCED DUCTILE MATRIX COMPOSITES

H.J. Böhm, W. Han, A. Eckschlager

Christian Doppler Laboratory for Functionally Oriented Materials Design,
Institute of Lightweight Design and Structural Biomechanics,
TU Wien, Vienna, Austria


Abstract - Three-dimensional periodic micromechanical models are used for studying the mechanical behavior of discontinuously reinforced ductile matrix composites. The models are based on unit cells that contain a number of randomly positioned and, where applicable, randomly oriented spherical, spheroidal or cylindrical reinforcements. The Finite Element method is used to resolve the microscale stress and strain fields and to predict the homogenized responses under overall uniaxial tensile loading in the elastic and elastoplastic regimes. Periodicity boundary conditions are employed in the analyses.

The main emphasis of the contribution is put on studying the microscale stresses in the reinforcements, which are evaluated in terms of both phase averages and ``inclusion averages''. The dependence of the inclusion averaged stresses on the fiber orientation is discussed for composites reinforced by randomly oriented short fibers, good agreement being found between unit cell and mean field models. For the case of spherical reinforcements the stresses in the particles are used to trigger brittle cleavage via a Weibull fracture criterion. The probabilistic algorithm can be used to model consecutive particle fracture in particle reinforced ductile matrix composites.


(hjb,040120)