Bladder-assisted resin transfer molding (BARTM) represents a well-suited process technology that enables flexible and efficient manufacturing of complex-shaped hollow composite parts. Here, controlled compaction and impregnation of the textile preform is a decisive factor during processing, which is, however, difficult to realize due to the variety of different process variants and adjustable manufacturing parameters. Hence, this thesis addresses the optimization of the injection stage of a specific pressure-controlled BARTM process that utilizes braided fabrics and reusable expandable bladders based on elastomeric materials. The selected methodical approach involves the development of basic analytical models that mathematically describe the relevant influencing parameters of the compaction and injection stage, which were verified by practical experiments. In particular, a novel application-oriented BARTM test rig was realized to investigate the filling behavior of tubular braided preforms under well-controlled process conditions. The use of a non-reactive substitution fluid as well as the implementation of a fully automated test procedure based on optical measurement methods enabled the execution of accurate and reproducible saturation experiments. The final task comprised a systematic evaluation of various process settings and the identification of an optimal parameter set that resulted in shortest filling times while maintaining a defined part quality. In order to describe the process-induced compaction state of the preform, a process model was established that allows for a prediction of relevant local compaction pressures during fluid injection. Saturation experiments conducted on different braided fabrics validated the feasibility of the new test method, which further enabled the characterization of the unsaturated apparent global permeability. It was shown that this parameter can be used to efficiently predict the filling behavior of tubular braided preforms. Based on the results obtained from the process optimization runs, a universal moldability diagram was derived that illustrates critical and admissible operating conditions within the technical limits of the BARTM system and supports in finding an optimal process setting.