PSI - Issue 77

Niels Grigat et al. / Procedia Structural Integrity 77 (2026) 365–375 Niels Grigat / Structural Integrity Procedia 00 (2026) 000 – 000

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represent a promising solution for hydrogen transport pipelines, combining low permeability with high mechanical integrity and corrosion resistance. 4.2. Simulation of Mechanical strength The mechanical performance of the developed FRP pipelines is investigated through numerical simulation in order to evaluate the influence of laminate configuration, layer orientation, and pipe geometry on the burst pressure. The simulation is conducted using finite element (FE) analysis, implementing detailed material models for both the fibre reinforced layers and the pipe core. The model takes into account the anisotropic behaviour of the reinforcement layers and the isotropic properties of the liner materials, thereby enabling an accurate prediction of stress distribution and failure initiation.

Figure 4.2: Assumptions for Preliminary Calculations – Mechanical strength The reinforcement layers, consisting of carbon and glass fibre composites, are modelled as transversely isotropic materials exhibiting linear-elastic behaviour. The failure of these layers is predicted using the Puck 2D Failure Criterion, which differentiates between fibre and inter-fibre failure modes. The model operates under the assumption that the composite reinforcement is insensitive to local buckling under internal pressure loading, a premise that can be attributed to the balanced laminate configuration. In contrast, the pipe core — composed of polyethylene (PE) and aluminium alloy (AL8011) — is defined as an isotropic structure following the von Mises stress criterion. It is assumed that full interfacial adhesion exists between the reinforcement layers and the liner, thereby ensuring effective load transfer across the composite wall. As illustrated in Figure 4.2, the sequence of applied layers and the definitions of materials are delineated. The simulation's primary focus is the internal pressure-induced stresses in the hoop and axial directions, with the objective of determining the burst pressure limits for a range of configurations. The laminate architecture exhibits variation in terms of the number of reinforcement layers, ranging from one to three, in conjunction with winding angles of ±54°, which are indicative of filament-wound structures. The findings indicate a significant correlation between the burst pressure and the number of reinforcement layers, as well as the inner pipe diameter (see Figure 4.3). Pipelines with three reinforcement layers have been shown to exhibit the highest predicted burst pressures across all diameters, reaching up to 140 bar for small-diameter pipes (~10 – 15 mm). As the diameter increases, the burst pressure decreases non-linearly, following the classical thin-wall pressure relationship. For single-layer structures, a significant decline in mechanical resistance is observed, particularly for diameters exceeding 40 mm. This finding underscores the necessity for multilayer reinforcement in large-scale applications. The findings of this study demonstrate that the mechanical integrity of FRP hydrogen pipelines can be tailored through laminate stacking and fibre orientation. Increasing the number of reinforcement layers or optimising their winding angle enhances pressure resistance without significantly increasing wall thickness, offering substantial weight savings compared to steel counterparts.