Assessing Optimal Fiber Trajectories during AFP Layup for Large Liquid Hydrogen Tanks

Kurzfassung

Automated Fibre Placement (AFP) offers greater flexibility than filament winding by enabling fibre steering and selective material deposition, allowing laminate architectures that can be tailored to the varying load requirements of composite pressure vessels. However, this increased manufacturing freedom introduces challenges associated with steering limits, fibre coverage, and gap formation on doubly curved dome geometries, making fibre trajectory design a coupled structural and manufacturing problem. This thesis develops a computational framework for the preliminary design of AFP-manufactured Type V composite liquid hydrogen pressure vessel domes. First, four canonical fibre trajectory formulations together with a new hybrid strategy are formulated and systematically assessed with respect to their manufacturability and structural characteristics using a curvature-weighted adaptive integration scheme for efficient trajectory generation. Subsequently, an analytical model is developed to rapidly evaluate laminate stiffness, structural mass, and Tsai--Wu failure indices, enabling efficient exploration of the design space during optimisation. The analytical framework is then integrated with a differential evolution algorithm to optimise laminate architecture, while selected optimum designs are assessed using finite element analysis. The results demonstrate that fibre trajectory selection, fibre placement angle, reinforcement distribution, and stacking sequence strongly influence structural performance. Among the investigated approaches, laminates employing variable-$\kappa_0$ constant-curvature and hybrid trajectories achieve the lowest structural mass while satisfying the design constraints. Finally, the findings are consolidated into AFP-specific layup guidelines that combine structural design principles with manufacturing considerations to support the preliminary design of lightweight composite liquid hydrogen pressure vessel domes.