FRACTURE AND SLIP OF INTERFACES IN CEMENTITIOUS COMPOSITES .2. IMPLEMENTATION

This paper focuses on the numerical treatment of an interface model that was presented in the companion paper. A generalized trapezoidal rule is proposed for integrating the slip rule. The new model is used in finite element predictions, whereby Newton iterations to achieve equilibrium require the algorithmic tangent stiffness matrix that is pertinent to the incremental problem. In order to ensure convergence to a physically acceptable (stable) solution, one should employ a modified tangent stiffness that is always positive definite. The analysis of a simple composite microstructure confirms that the model is capable of predicting interface failure. Application of the interface model as a generalized fictitious crack model concludes the paper. Preliminary results show that it is possible to obtain a crack pattern that extends from the aggregate-mortar boundary into the mortar itself along predefined interelement boundaries.