### Monday, 11 October 2004 - 1:25 PM

### This presentation is part of : Mechanics of Fiber Networks and Fibrous Materials

### Effective electromechanical properties of a fiber-reinforced cement based material

Yeranuhi Hakobyan, **Katerina D. Papoulia**, and Mircea D. Grigoriu. Cornell University, Department of Physics, Clark Hall, Ithaca, NY 14853
We explore the capability of a cement based weak conductor for sensing damage and strain. The material is reinforced by small (5 mm long, 15 microns in diameter) carbon fibers. In this context we formulate a method for representing and analyzing random heterogeneous materials in three directions. General probabilistic models are developed for the microstructure of cement-based composites with carbon fibers. The models are random fields characterizing the geometrical, mechanical, and electrical properties of the material constituents. We describe our computational environment for calculating the evolution in time of the properties of microstructures subjected to deterministic loads. Finite element procedures are used to calculate changes in the stress, strain, damage and electric fields in cement-based composite specimens generated from their probabilistic models. The problem entails advances in numerical solver techniques and formulation of new mathematically sound traction-displacment relationships to model cohesive fracture. A percolation study based on a fiber network is conducted. The results of the finite element analyses are used to update the probabilistic models of the material microstructure so they reflect the current damage state. The evolution of the material state is monitored by a mathematical object that defines uniquely the state of the microstructure at any time during loading and can be stored in the computer. The results of the analytical and numerical developments are validated against experimental tests providing information of the properties of the fiber-matrix interaction and on the dependence of electric conductivity of macroscopic specimens on their damage state.

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