PSI - Issue 82

Abhijit Joshi et al. / Procedia Structural Integrity 82 (2026) 91–97 A. Joshi et al./ Structural Integrity Procedia 00 (2026) 000–000

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Bonora and Ruggiero, 2005; Cavallini et al., 2008; Collini and Pirondi, 2019). In this paper, the analysis is performed with the former approach. Such modelling is a good starting point since the Young’s modulus of graphite is approximately 1/10 th of that of the surrounding matrix and it covers the possibility that graphite particles could be debonded from the matrix under the applied loads. Additionally, graphite does not experience any creep in the 400 °C to 500 °C temperature range. 2.1. Geometry, mesh, loads and boundary conditions The 2D RVE model used in the simulation includes the matrix domain of 100 µ m x 100 µ m dimension. The material properties and creep-simulation approach were first validated with the model formed only by the matrix. After this validation, analysis was completed with graphite particle modelled as a circular void. The average volume fraction of graphite particles for the material used in this research was 9.04%, which is equivalent to a circular void of radius 16.96 µ m. The geometric details of these two models are shown in Figs. 2a and 2b along with mesh details for the model with circular void presented in Fig. 2c. The models were meshed with 8-node quadratic 2D plane stress element CPS8. Based on the mesh-sensitivity studies, a typical elements size of 0.75 microns was used in the analysis. The load history used in the simulations is shown in Fig. 3a. The load was ramped up from 0-15 N in 0.01 hour (36 seconds) and was held steady for 100 hours to allow creep deformation. The load ramp up time is representative of actual loading in the in-house creep test. The load of 15 N generates 150 MPa macroscopic stress in the model. The boundary conditions for the model are given in Fig. 3b. A rigid point was introduced in the model above the matrix, which, along with the kinematic couplings in the Y direction ensures a uniform displacement at the top face of the matrix. The bottom face of the matrix was restrained in the Y direction to react to the applied load. The rigid point and the midpoint of the bottom face of the matrix were restrained in the X direction to prevent the rigid-body motion of the model.

Fig. 2. Geometry for models with matrix only (a) and graphite particle modelled as circular void (b); (c) mesh for model (b).

Fig. 3. (a) Load history; (b) boundary condition used in creep simulations.