PSI - Issue 77

Kumar C. Jois et al. / Procedia Structural Integrity 77 (2026) 405–412 Jois, et al./ Structural Integrity Procedia 00 (2026) 000–000

408

4

3

2

Internal Pressure

ϴ

1

YSYMM U2=UR1=UR3= 0

XSYMM U1=UR2=UR3 =0

ZSYMM U3=UR1=UR2 =0

Fig. 2. Load and boundary conditions for full layup without cohesive surfaces [1].

An XSYMM boundary condition was applied to the side surface indicated by arrows, constraining displacements along the 1-direction and suppressing rotations about the 2- and 3-axes. The YSYMM boundary condition, applied to the rearward face, fixed the angular orientation between the 1- and 2- directions (θ = 6°) and prevented rotations about the 1- and 3-axes. Similarly, the ZSYMM boundary condition was imposed on the bottom surface, restricting displacements in the 3-direction and inhibiting rotations about the 1- and 2-axes. These boundary conditions ensure geometric symmetry and mechanical compatibility across the modelled domain, enabling a representative simulation of the pressure vessel’s response under internal loading. The material properties are provided in the Table 1.

Table 1: Composite constitutive properties. [MPA] [MPA] [MPA] [-]

[-] [-] [MPA] [MPA] [MPA]

143970

7450

7450

0.27

0.27

0.21

5600

5600

3700

Cohesive surface elements were employed to model the interlaminar interactions between composite layers. For regions containing voids, the corresponding elements or element groups were assigned a hard contact condition, while the remaining interfaces retained the cohesive properties. The void assignment was automated using a Python script, enabling the generation of multiple models with varying void distributions for comparative analysis. In order to assign realistic epoxy damage initiation and evolution properties (see to the cohesive surface, data from Jois et al. [10] was implemented, although the stiffness values were chosen for convergence purposes and the normal traction, t n , had to be increased for the same reason. Also, in all cohesive simulations a viscous term equal to 0.001 has been included to facilitate convergence.