B4/II Failure simulation of structures at impact loading strengthened by mineral-bonded composite layers
Numerical modeling of concrete behavior faces numerous challenges due to its unsymmetric response in compression and tension and due to its quasi-brittle nature at failure. This characterization becomes even more complex at impact loads, where rate effects considerably change concrete properties. To simulate this behavior, a robust algorithm that models fracture in the variational sense will be implemented and a material model that mimics the physics of this behavior will be formulated.
The eigenerosion approach is a numerically efficient and stable realization of the variational eigenfracture scheme. Due to its regularization via the crack neighborhood, localization and mesh dependency are generally avoided. The material description developed in the first GRK 2250 cohort (Project B4), which includes a consistency viscoplastic constitutive formulation in the microplane framework, is suitable to predict a wide range of concrete material characteristics at high loading rates.
Crack propagation represented by the eigenerosion approach for a) a CT-specimen (Qinami, Pandolfi, Kaliske, IJNME 2019), b) impact on concrete plate.
Further development of the eigenerosion approach should be carried out for Strain-Hardening Cement-Based Composites (SHCC), where the effects of fibres in crack-bridging should be considered. A major step forward for the variational eigenfracture scheme will be the introduction of a meshfree spatial discretization in terms of the Material Point Erosion scheme. The implementation of a meshfree method requires efficient approaches for the computation of the shape funtions and adequate solution strategies to perform numerical integaration at the boundaries. The method would be able to model phenomena like penetration and multiple spalling and to circumvent numerical problems, which arise from distorted meshes. The final goal of the project will be the development of a numerical approach that can model impact on strengthened plates by the use of the Finite Element Method (FEM) and Material Point Erosion.