Correlation between the internal length, the fracture process zone and size effect in model materials

K Haidar,G Pijaudier-Cabot,J F Dubé,A Loukili

doi:10.1007/bf02479345

Abstract

In this paper, we examine the correlation between the width of the fracture process zone, the parameters entering in the description of size effect (related to the dimension of the specimen especially), and the internal length in non local constitutive relations for a model mortar material with a controlled macro-porosity. Experimental investigations on this material in compression, bending, acoustic emission measurements and their analysis are detailed. The experiments show a good agreement between the evolution of Bažant's size effect parameterd 0 and the evolution of the width of the FPZ. The internal length obtained with the help of inverse finite element analysis is also proportional to these quantities. This correlation provides a reasonable approximation of the internal length, from an experimental test on specimens of a single size directly, equipped with acoustic emission localization devices.

Highlights

In quasi-brittle materials, fracture exhibits a fmite size fracture process zone (FPZ)
The results revealed that micro-cracking occurs randomly around the macro-crack and that the FPZ expands after peak load due to the presence ofaggregates
The aim ofthis contribution is to examine the experimental correlation between the width of the fracture process zone observed with AE analysis, the parameters entering in the description of size effect, and the internal length in non local constitutive relations

Summary

INTRODUCTION

In quasi-brittle materials, fracture exhibits a fmite size fracture process zone (FPZ). This internal length can be related to the width of the fracture process zone [4,5,6] Those constitutive theories do predict size effect on the structural strength. One of the open issues in non local modeling is direct measurement of this internal length or, in other words, experimental techniques which aim at observing the fracture process zone. The aim ofthis contribution is to examine the experimental correlation between the width of the fracture process zone observed with AE analysis, the parameters entering in the description of size effect, and the internal length in non local constitutive relations. Where db is the density of the desired mixture, d., is the density of the reference mortar, and dp is the density of the polystyrene beads

EXPERIMENTS ON MORTAR AND MODEL MATERIALS

CORRELATION WITH THE INTERNAL LENGTH

Findings

CORRELATION WITH EXPERIMENTAL DATA