Calculation of the critical stress in two-phase materials

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One of the primary reasons for the observed deviation of the behaviour of concrete from predictions based on linear elastic fracture mechanics can be the interaction between a crack and a material inhomogeneity such as a particle which necessarily exists in such a material. In this paper, concrete is modelled as a two-phase material and the behaviour of a crack with its tip on the interface between two different materials is studied. In contrast to cracks in homogeneous materials the stress singularity for a crack terminating at the interface is of the type r exp -lambda, where the value of the stress singularity exponent, lambda, is in the interval 0 < lambda < 1. This means that classical fracture mechanics theory and criterion cannot be applied. In the paper a new stability criterion is formulated. Conditions for the stability of the crack terminating at the interface between two materials are then used to estimate the critical stress for the intersection of coarse aggregate particles. It is shown that the value of the critical stress depends on the elastic mismatch for both components. The application of the suggested procedure will contributes to a reliable evaluation of the critical fracture parameters of concrete.

aggregate, cement paste, concrete, critical stress, elastic mismatch, finite element method, fracture mechanics, mortar, two-phase material

KNÉSL, Z., NÁHLÍK, L., KERŠNER, Z.

2002

2. 4. 2001

ELSEVIER SCIENCE Ltd.

Amsterdam

0-08-043948-9

Structural Engineering, Mechanics and Computation

1

737

744

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