Interface Element Modeling of Fracture in Aggregate Composites

Abstract

A brittle aggregate composite such as portland cement concrete or mortar is modeled in two dimensions as a system of perfectly rigid particles of various sizes separated by interface layers that are characterized hy a given force-displacement relation for the normal and tangential components. The force-displacement relation exhihits for the normal component a tensile strength limit followed hy a sudden drop of force to zero. The system of rigid particles is generated randomly. The particles arc not allowed to overlap and are generally not in contact; however. when the distance hetween the particles is less than a certain limit, a deformahle interface layer is introduced. Numerical simulation of a fracture specimen with a notch shows that the fracture front consists of an irregular band of interparticle cracks the width of which is ahout three maximum particle sizes. The interparticle cracks remain continuous and do not coalesce into a continuous line fracture until the deformation is very large. The load-displacement relation exhihits gradual softening after the peak force. with a rapid force decrease followed by a long tail of slowly decreasing force. These features qualitatively agree with observations of concrete.

Scaling of structural failure

“…An arbitrary Poisson ratio and a wider damage band can be achieved by a particle model in which the links between particles transmit not only axial forces but also shear forces. This is the case for the model of Zubelewicz (1983) and Zubelewicz and Baiant (1987), as well as the model of Schlangen and van Mier (1992) and van Mier and Schlangen (1993). In the latter, the particle system is modeled as a frame with bars that undergo bending (the bending of the bars is of course fictitious and unrealistic, but it does serve the purpose of achieving a shear force transmission through the links between particles).…”

A MLS-Based Lattice Spring Model for Simulating Elasticity of Materials

“…Given the geometry data of the lattice spring model, 2D α can be estimated through: (29) where i l is the original length of the ith bond. Equations (27) and (28) Compared to the displacement results obtained by FEM, the maximal relative errors of CLSM and DLSM (denoted as Err_1 and Err_2) are given in Table 1 for four different values of Poisson's ratio.…”

Particle Model for Quasibrittle Fracture and Application to Sea Ice

“…The size of the particles should be proportional to the characteristic length of the material determined by the size of major inhomogeneities. For example, in the model for concrete developed by Bazant et al (1990) and Zubelewicz and Bazant (1987), the particles represent large aggregates and are assumed to be perfectly rigid. Elastic deformation, damage, and fracture are reflected by changes in links connecting neighboring particles.…”

“…An extension of Cundall's rnethod to the study of microstructure and crack growth in geomaterials with finite interfacial tensile strength was introduced by Zubelewicz (1980Zubelewicz ( , 1983, Zubelewicz and Mr6z (1983), and Plesha and Aifantis (1983). As dernonstrated by Zubelewicz and Bazant (1987), a particle model sirnulating the rnicrostructure of an aggregate cornposite such as concrete can describe progressive distributed microcracking with gradual softening and with a large cracking zone. This rnodel was modified and refined by Bazant et al (1990), who used it in a study of the size effect on the norninal strength and on the postpeak slope of load-deflection diagrarns.…”