Doctoral Researcher
Alaleh Shehni

Modelling fiber-matrix bond and cement based composites under impact loading

The aim of this subproject is to make a numerical model of cement based composites which fibers are modeled explicitly and represented by embedded elements.

To this aim, our in-house program CaeFem has been developed to analyze simple regular discretization of heterogeneous mesoscopic continuum with discrete distinction of aggregates or void from a matrix with different discretization approaches and comparisons are made with a commercial FEM program-DIANA. A material model is implemented and assigned to bond element to connect embedded fibers to continuum which fibers are distributed randomly within the simply discretized continuum. The next three steps will be: modeling of random geometry (for position, orientation and length of fibers, position and size of aggregates, comparison of approaches to model continuum with embedded fibers and embedded smeared or discrete cracks using FEM (SDA and X-FEM), EFG and iso-geometric methods and implementation of physical nonlinearities regarding fiber, bond, aggregates, matrix. Incidentally, the behavior of composite under quasi-static loading, as a necessary prerequisite for dynamics, will be validate by experiment results provided by Institut für Baustoffe.

Irregular mesh used for Fem method
Regular mesh used for mesh-free methods

 

Current challenge:
Modelling the behavior of high strength SHCCs (Strain-hardening cement-based composites) made with high performance polymer fibers under quasi-static tensile loading. High density polyethylene fibers are modelled explicitly and distributed randomly in a two-Dimensional model. Single fiber pullout test result is used for micromechanical characterization of bond strength. Load test simulations are conducted with in-house program CaeFem and comparisons will be made with experimental results. Several sensitivity analysis will perform based on different fiber contents and notches located in the mid-height of a dumbbell specimen. The resultant behaviors will be compared and verified versus obtained results from.

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a) Thin dumbbell specimen and Test set-up, b) Specimen with notch, c) Simulation of notch area and d) Crack pattern for notch model under quasi static tensile loading.

 

Publications
Shehni, A., Häußler-Combe, U., 2018. New approach on discretization methods for mesoscopic study of concrete structures. In 6th European Conference on Computational mechanics (ECCM 6) 7th European Conference on Computational Fluid Dynamic (ECFD 7), 11-15 June, 2018, Glasgow, (UK).

Häußler-Combe, U., Chihadeh, A., Shehni, A., 2019. Modelling of discrete cracks in reinforced concrete plates with the strong discontinuity approach (SDA). Submitted to the 7th International Conference on Structural Engineering, Mechanics and Computation SEMC 2019.

Shehni, A., Häußler-Combe, U., Curosu, I., Gong, T., Mechtcherine, V. 2019. Numerical simulation of HS-SHCC under quasi-static tensile loading. In Pijaudier-Cabot et al. (eds.) 10th International Conference on Fracture Mechanics of Concrete and Concrete Structures FraMCoS-X, 23-26 June, 2019, Bayonne, France.

 

03. – 05.02.2020
Third GRK2250/1 Workshop

Call for Applications

There are 11 open vacancies for doctoral researchers for the second cohort of the project - GRK 2250/2, which will start in May 2020. Interested and motivated candidates are welcome to apply before 13.12.2019. More detailed information can be found here.

Contact


TU Dresden
Institute of Construction Materials
01062 Dresden, Deutschland
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