Material characterization for compression resin transfer molding process simulation

Compression resin transfer molding (CRTM) has been shown to be a promising manufacturing process for automotive applications. CRTM optimization via simulation has been subject of various studies, yet these studies do not adequately assess the material characterization used to get their simulation input. The present paper aims to close this gap by presenting methods for characterizing the resin and reinforcement phase, then discussing test results for two typical automotive materials. An epoxy resin system was characterized by viscosity measurements using a rotational rheometer. The viscosity was observed to remain at a low level for a certain transition time, followed by an exponential rise. This transition time decreased with increasing temperature. In-plane and out-of-plane permeability tests with the chosen biaxial carbon fiber non-crimp fabric (NCF) were performed for fiber volume fraction (FVF) ranging from 40% to 60%, showing a strong dependency between FVF and permeability. The compaction behavior of the NCF was characterized for two compaction rates. Observed differences in the stress-strain curves indicate viscoelastic compaction behavior. The present study demonstrates that the utilized test methodologies are suitable to characterize the input parameters needed for CRTM simulation. Using the presented material database as simulation input provides a starting point for future CRTM software verification and process optimization.