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Closed mold injection processes such as resin transfer molding have an increasing importance for manufacturing high quality carbon fiber reinforced parts at high production rates. One major challenge during this process is to avoid resin rich corners, which are a result of a non-uniform compaction of the preform in the tool. The objective of this work is to predict compaction defects in the preform and their effects on the filling behavior. We use numerical compaction simulations to calculate the preform geometry after tool closing, which is subsequently transferred into the infiltration simulation to model the filling behavior. Additionally, the fiber volume content and the material orientations are transferred from the mechanical simulation. Areas in the tool, which are not filled by the reinforcement, are modelled as flow channels with high permeability. The achieved results prove the significant influence of the compaction state on the filling behavior. The novel method supports the design of RTM tools and helps to optimize the manufacturing process.

This study presents a numerical method for optimizing the quantity and the placement of reinforcements along the principal-stress trajectories. The model representing carbon fiber composite structures consists of solids and embedded one-dimensional beam elements. Based on the Runge-Kutta method, the reinforcing structure is optimized considering the manufacturability of additive manufacturing (AM). For a case study, the optimization method is performed on an open-hole specimen. The Young’s modulus and the tensile strength of the optimized structure show an increase of more than 30 % and ~50 % in the simulation, respectively, compared to the reference specimen from another study. Robotic additive manufacturing is used to fabricate the specimen for experimental validation. The prediction of absolute values of tensile strength are reliable comparing to the experimental test, however, there is a deviation of more than 30 % in the linear-elastic behavior possibly due to the presence of voids in the printed part.

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