PSI - Issue 82

Igor Guz et al. / Procedia Structural Integrity 82 (2026) 239–245 I. Guz et al./ Structural Integrity Procedia 00 (2026) 000–000

242

4

Fig. 3. Sandwich pipe configurations.

The pipes are subjected to high external pressure relevant to offshore piping. Two thermal cases are considered: high uniform temperature, T=80 o C; and internal surface temperature, T i =80 o C, with the outer surface exposed to convection (surrounding temperature T ∞ =4 o C and heat transfer coefficient h=50Wm -2o C -1 ). The latter is illustrative of a deepwater application in which the pipe contents are hotter than the surroundings. Initial T ref =25°C is assumed. Temperature distributions for the T i =80°C case are shown in Fig. 4. The gradient is steeper through PVC than epoxy due to lower conductivity.

Fig. 4. Temperature distributions: T i = 80°C.

Cylindrical stress distributions for uniform and thermal gradient cases are shown in Fig. 5 and Fig. 6 respectively. The applied pressures are P e =15MPa and P i =10MPa. Lowering core density increases the disparity between inner and outer skin axial, hoop and shear stresses. The HP60 configuration exhibits the largest stress magnitudes in the outer skin and is the only configuration for which the hoop component is tensile in the inner skin. Compared to the epoxy configuration, the HP250 configuration displays comparable inner skin response and only slightly higher stresses in the outer skin but weighs less than half the mass (2.12kg/m versus 5.36kg/m). In the radial direction the magnitude of compressive stress through the core is lower than the applied pressure in the case of a low-density core. Overall, stresses for the graded core pipe are in between those of the lighter and heavier counterparts. Stresses for larger external pressure, P e =20MPa, are shown in Fig. 7 and Fig. 8. Compared to the lower pressure the skin plies are more utilised; compressive stress magnitudes in the inner and outer skins are greater and in the inner skin of the HP60 configuration the hoop stress has switched from positive sign to a small negative value. There is greater disparity between inner and outer skin responses particularly for the low-density configuration.