TY - GEN

T1 - Micro-meso-macro modelling of composite materials

AU - Wriggers, Peter

AU - Hain, M.

PY - 2007

Y1 - 2007

N2 - Multi-scale models can be helpful in the understanding of complex materials used in engineering practice. Applications related to this class of problems covers different length scales in the range from μm to m. Using the concept of representative volume elements (RVE), the theoretical background is discussed in this contribution as well as the numerical treatment of the resulting three-dimensional RVEs. The developed methodology is applied to a specific engineering material which is concrete. This construction material has to be investigated on three different scales: the hardened cement paste (hcp), the mortar and finally the concrete. Here, a successive two-stage approach is followed in which first the multi-scale model of hcp and mortar is applied. The resulting homogenization can then be used in the next step for a multi-scale mortar-concrete model. At the micro-scale of hcp, a finite element mesh based on a three-dimensional computer-tomography with different constitutive equations for the three parts unhydrated residual clinker, pores and hydrated products is introduced. With respect to the finite element solution, homogenization techniques are used in order to calculate effective elastic material properties. The constitutive equations at the micro-scale contain inelastic parameters, which cannot be obtained through experimental testings. Therefore, one has to solve an inverse problem which yields the identification of these properties. For computational efficiency and robustness, a combination of the stochastic genetic algorithm and the deterministic Levenberg-Marquardt method is used. In order to speedup the computation time significantly, all calculations are distributed automatically within a network environment. Inelastic behavior occurs when the micro-structure hcp is filled partly with water and a freezing process takes place. A constitutive model for ice is applied to the water filled parts of the micro-structure. The expansion of the ice leads to damage in the hcp which is associated with inelastic material behavior. If such a calculation is performed for different moisture and temperatures, a correlation between moisture, temperature and the inelastic material behavior can be obtained. The effective constitutive equation of hcp will serve as a basis for a multi-scale mortar-concrete model.

AB - Multi-scale models can be helpful in the understanding of complex materials used in engineering practice. Applications related to this class of problems covers different length scales in the range from μm to m. Using the concept of representative volume elements (RVE), the theoretical background is discussed in this contribution as well as the numerical treatment of the resulting three-dimensional RVEs. The developed methodology is applied to a specific engineering material which is concrete. This construction material has to be investigated on three different scales: the hardened cement paste (hcp), the mortar and finally the concrete. Here, a successive two-stage approach is followed in which first the multi-scale model of hcp and mortar is applied. The resulting homogenization can then be used in the next step for a multi-scale mortar-concrete model. At the micro-scale of hcp, a finite element mesh based on a three-dimensional computer-tomography with different constitutive equations for the three parts unhydrated residual clinker, pores and hydrated products is introduced. With respect to the finite element solution, homogenization techniques are used in order to calculate effective elastic material properties. The constitutive equations at the micro-scale contain inelastic parameters, which cannot be obtained through experimental testings. Therefore, one has to solve an inverse problem which yields the identification of these properties. For computational efficiency and robustness, a combination of the stochastic genetic algorithm and the deterministic Levenberg-Marquardt method is used. In order to speedup the computation time significantly, all calculations are distributed automatically within a network environment. Inelastic behavior occurs when the micro-structure hcp is filled partly with water and a freezing process takes place. A constitutive model for ice is applied to the water filled parts of the micro-structure. The expansion of the ice leads to damage in the hcp which is associated with inelastic material behavior. If such a calculation is performed for different moisture and temperatures, a correlation between moisture, temperature and the inelastic material behavior can be obtained. The effective constitutive equation of hcp will serve as a basis for a multi-scale mortar-concrete model.

UR - http://www.scopus.com/inward/record.url?scp=84962891373&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84962891373

SN - 9781402065767

T3 - Computational Methods in Applied Sciences

SP - 105

EP - 122

BT - Computational Plasticity

A2 - Onate, Eugenio

A2 - Owen, Roger

PB - Springer Netherlands

T2 - 8th International Conference on Computational Plasticity, 2005

Y2 - 5 September 2005 through 8 September 2005

ER -