Adaptive multiscale modeling and analysis of nonlinear thermoelastic composites

• Applicant: Professor Dr.-Ing. Peter Wriggers
• Subject Area: Mechanics
• Term: from 2007 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 35286377

• Final Report Year: 2015

Final Report Abstract

This work established a reliable multiscale multiphysics model to analyze failure of concrete due to alkali-silica reaction (ASR) and to the weak properties of the interfacial transition zone (ITZ). The mesostructure of concrete consists of aggregates with a random distribution embedded in a homogenized hardened cement paste (HCP) as well as interface elements with zero-thickness as the representation of the ITZ. One scale lower, the microscale constitutes the finest structural scale and is represented by the microstructure of the HCP obtained from three-dimensional computed tomography (CT) scans, which is comprised of hydration products, unhydrated residual clinker and micropores. This work constructed a multiscale model to predict the deterioration due to ASR in concrete with the goal of accelerating the prediction of the extent of damage in comparison to experimental procedures. Based on a correlation between the effective damage and the chemical extent, the simulation of ASR induced deterioration at the mesoscale was carried out through a coupled diffusion-thermal-chemical-mechanical framework in a staggered setting, yet upscaling the chemical damage quantity from the microscale during the process. Computational thermal homogenization with statistical tests was applied to obtain the effective thermal conductivity of HCP, thus enabling to identify the macroscopic thermal conductivity of concrete efficiently. The microstructure of the ITZ with higher porosity yields its weak mechanical properties. In this work, a cohesive zone model (CZM) was used to describe the debonding at the ITZ between HCP and aggregates. Also, the influence of various parameters on the macroscale mechanical behavior of concrete was analyzed. A scalar interface damage parameter was defined in the interface elements in order to quantify how much they debond in tension and in compression respectively. Apart from the mechanical problem, the influence of the interface crack on the thermal conduction as well as humidity diffusion was also investigated. The traction-separation law in CZM combined with micromechanically motivated thermal fluxseparation relation and diffusion flux-separation relation was established, thereby leading to the temperature jump and humidity jump across the cohesive crack.

Publications

• Chemo-thermo-mechanics coupling applied in hardened cement paste, Proceedings in Applied Mathematics and Mechanics.10:391–392, 2010
  T. Wu and P. Wriggers
  
• A method of two-scale chemo-thermalmechanical coupling for concrete. Proceeding of Computational Pasticity XI: Fundamentals and Applications, Barcelona, Spain, 1626–1637, 2011
  T. Wu, I. Temizer and P. Wriggers
  
• An adaptive multiscale resolution strategy for the finite deformation analysis of microheterogeneous structures, Computer Methods in Applied Mechanics and Engineering, 200, 2639-2661, 2011
  I. Temizer, P. Wriggers
  
• Computational homogenization of damage in the hardened cement paste due to alkali silica reaction. Proceedings in Applied Mathematics and Mechanics, 11:561 – 562, 2011
  T. Wu, I. Temizer and P. Wriggers
  
• Multiscale modeling of Alkali-Silica Reaction induced damage in concrete: coupled hydro-chemical and thermo-mechanical effects. Proceeding of 10th World Congress on Computational Mechanics, Sao Paulo, Brazil, 1-7, 2012
  T. Wu, I. Temizer and P. Wriggers
  
• A Multiscale method to analyze the deterioration due to Alkali-Silica Reaction considering the effects of temperature and relative humidity, Proceeding of V Coupled Problems Conference, Ibiza, 2013
  T. Wu, I. Temizer and P. Wriggers
  
• Computational thermal homogenization of concrete. Journal of Cement and Concrete Composites, 35:59-70, 2013
  T. Wu, I. Temizer and P. Wriggers
  
• On the optimality of the window method in computational homogenization, International Journal of Engineering Science, 64:66-73, 2013
  I. Temizer, T. Wu and P. Wriggers
  
• Effects of debonding on thermal conduction and humidity diffusion at mesoscale of concrete. Proceedings in Applied Mathematics and Mechanics, 14, 489-490, 2014
  T. Wu and P. Wriggers
  
• Multiscale hydro-thermo-chemo-mechanical coupling: application to Alkali-Silica Reaction, Journal of Computational Material Science, 84:381-395, 2014
  T. Wu, I. Temizer and P. Wriggers
  
• Multiscale diffusion–thermal–mechanical cohesive zone model for concrete. Computational Mechanics, May 2015, Volume 55, Issue 5, pp 999–1016
  T. Wu and P. Wriggers