Composite manufacturing is currently one of the most challenging processes for industrial lightweight applications. To date, the process conditions for polymer-based composite manufacturing are evaluated by laboratory measurements: usually, the flow behavior and the curing of the polymer matrix material are characterized by rheology and quality assurance is performed by thermo-physical analysis in postprocess measurements. In contrast a dielectric in-mold sensor offers the possibility to measure the real-time behavior of the polymer during processing. This study focuses on the correlation of simultaneous rheological and dielectric measurements on Hexcel RTM6 using a coupled setup of both techniques. For dielectric measurements a reusable in-mold sensor was used and a calibration, taking into account the cable response, was performed. The results show good agreement with respect to glass-transition temperature and the gel-point. This can be understood by the fluctuation-dissipation theorem that explicitly relates molecular dynamics to the macromolecular mechanical properties under dynamic time-dependent load. Furthermore, it was found that the dynamic viscosity can directly be related to the electrical conductivity. This proves the high potential of dielectric analysis as online-capable technique for material characterization during composite manufacturing. V C 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 907-913

The aim of the present work was to establish a cure‐prediction via dielectric analysis (DEA) for a bisphenol A diglycidyl ether (DGEBA) epoxy cured with an imidazolium‐based ionic liquid [EMIM][N(CN)2]. Ionic liquids caught increasingly attention in the composite industry due to their potential use as efficient latent curing agent and hence possible optimization of production cycles. Dielectric analysis is a promising tool for mass‐scale composite production for monitoring cure and as feedback control system, however a profound correlation to thermal and rheological properties is necessary. For this purpose, complementary cure kinetic modeling of the neat system was first carried out via differential scanning calorimetry (DSC) to allow the prediction of the degree of cure and glass transition temperature Tg during the curing cycle. The focus laid on the comparison between isoconversional and model‐based prediction and the influence of the implementation of the diffusion factor. Dielectric measurements were conducted and afterwards a cure prediction based on these results was established. Problems with ionic liquids as curing agent along with using DEA as characterization method were addressed. Consequently, to verify the previously obtained outcome, dielectric analysis was conducted to real‐time monitor the crosslinking during the resin transfer molding (RTM) process. Sufficient agreement to theoretical cure prediction based on DSC and DEA results with actual conversion during RTM was observed.