Modeling of damage in cementitious materials at the microstructural scale: characterization by experimental imaging and 3D numerical simulations
PhD candidate: Thanh Tung NGUYEN
Defended : November 5, 2015
Advisors: Julien YVONNET (MSME), Qizhi ZHU (MSME), Michel BORNERT (NAVIER), Camille CHATEAU (NAVIER)
Thanh Tung NGUYEN has been awarded the 2015 CSMA price of best PhD in computational mechanics in France in 2015.
Brief summary of the project
In this PhD, we have developed methodologies to model microcracking in realistic microstructures of civil engineering materials by combining advanced numerical simulation approaches and experimental 3D imaging techniques (micro CT-scan) to follow the cracks during in-situ mechanical testing. The following results have been obtained
- The first applications of the numerical phase field method to model complex crack initiation and propagation within realistic microstructures obtained from micro CT scans;
- Extension of the phase field method to interfacial damage;
- The first direct comparisons between 3D crack network obtained by experiments and numerical simulations;
- A procedure to identify the microstructural damage parameters by inverse approaches, by combining the numerical simulations and the experimental results.
Figure 1: (a) A cylindrical sample plaster embedding PS beads; (b) Experimentally observed cracks during in-situ compression test within a microtomograph; (c) numerical simulation of cracking using the phase field method 
Figure 2: (a) Microtomography of the cylindrical sample of lightweight concrete showing pores (in black), sand grains (in dark grey) and plaster matrix (in light grey); (b) sub-volume studied during the experiment (in situ compression test); (c) geometry of the phase in the sub-volume; (d) comparisons of 3D crack propagation between experiments and numerical simulations for different loads .
Publications in international journals
 T.T. Nguyen, J. Yvonnet, Q.-Z. Zhu, M. Bornert, C. Chateau, Initiation and propagation of complex 3D networks of cracks in heterogeneous quasi-brittle materials: direct comparison between in situ testing- microCT experiments and phase field simulations, Journal of the Mechanics and Physics of Solids, 95:320-350, 2016
 T.T. Nguyen, J. Yvonnet, M. Bornert, C. Chateau, K. Sab, R. Romani, R. Le Roy, On the choice of numerical parameters in the phase field method for simulating crack initiation with experimental validation, International Journal of Fracture, 197(2), 213-226, 2016.
 T.T. Nguyen, J. Yvonnet, Q.-Z. Zhu, M. Bornert, C. Chateau, A phase-field method for computational modeling of interfacial damage interacting with crack propagation in realistic microstructures obtained by microtomography, Computer Methods in Applied Mechanics and Engineering, 312:567-595, 2016
 T.T. Nguyen, J. Yvonnet, Q.-Z. Zhu, M. Bornert, C. Chateau, A phase field method to simulate crack nucleation and propagation in strongly heterogeneous materials from direct imaging of their microstructure, Engineering Fracture Mechanics, 139:18-39, 2015.