PSI - Issue 66

Mansi Gupta et al. / Procedia Structural Integrity 66 (2024) 122–134 Mansi Gupta et al. / Structural Integrity Procedia 00 (2025) 000 – 000

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Fig. 7. Displacement contour in z-direction at (a) 0 ps, (b) 600 ps, (c) 1095 ps.

6. Fracture Characterisation The MD simulations are suited for the fracture analysis of materials due to the fact that the complete fracture process can be modelled in picoseconds. The mode I fracture is commonly used for fracture testing and is simulated here. The stress-strain curve, fracture energy, and fracture toughness are crucial parameters in understanding the mechanical and fracture behaviour of CSH gel. The stress-strain curve in Fig. 9 provides insight into the mechanical response of C-S-H gel under applied stress. The post-peak softening of material can be seen from the curve. The spikes in the presented curve are due to the continuous rearrangement of atoms and molecules. Breaking of atomic bonds results in sudden decrease in stress while the bonding of atoms leads to increase in stress levels. In the initial part of the curve, the stress increases almost linearly with strain. The slope of this part corresponds to the Young's modulus, which indicates the stiffness of the material. It should be noted that the peak value obtained from the MD simulation is higher than the peak stress observed in actual macroscale experiments. It is due to the fact that more energy is required at nanoscale to overcome the bond dissociation energy. Although the load values are less suitable for predicting the macroscale properties, but through multiscale modelling the macroscopic response of the structure can be accurately predicted. Here, the scope of this work is limited only to nanoscale modelling only and discussion on the fracture toughness and energy has been made to understand the bond breaking characteristics.