Characterizing and modelling the time-dependent compaction response of an infiltrated binder-stabilized unidirectional non-crimp fabric

In wet compression molding (WCM), understanding the compaction behavior of infiltrated reinforcement fabrics is essential, as it impacts the microstructure and fiber volume fraction of the finished part. Incorporating binder-stabilized reinforcements may be necessary in WCM to improve material handling and enhance part quality. This research aims to characterize and model the time-dependent compaction behavior of an infiltrated, binder-stabilized carbon fiber unidirectional non-crimp fabric (UD-NCF) through multi-phase experiments, specifically focusing on effects of resin viscosity, stacking sequence, and binder pre-activation. Findings indicate that infiltrated fabric requires lower compaction forces compared to dry fabric, mainly due to the lubrication of tows and stitching, which reduces tow-stitch friction and provides less resistance to tow spreading. Furthermore, compaction forces increase with binder pre-activation across all conditions tested, while the degree of relaxation is reduced. Lastly, the stacking sequence has a minor influence on the compaction response owing to limitations in tow nesting imposed by supporting fibers. Maxwell and fractional Zener models are considered to capture the fabric time-dependent response, with the latter providing an improved fit to the experimental data. This is the first detailed investigation on compaction behavior of infiltrated, binder-stabilized UD-NCFs, offering new and important insights into their complex deformation response.