Dynamic-mechanical-thermal analysis of hybrid continuous–discontinuous sheet molding compounds

Sheet molding compounds (SMC) are very promising for the production of lightweight structural components, due to the specific mechanical properties combined with the suitability for a large-scale manufacturing process. Automotive industry already implements SMC materials for structural components in their vehicle concepts. Polymeric materials, hence also fiber reinforced polymers, show a viscoelastic behavior and dynamic-mechanical-thermal analysis (DMTA) is an important method of determining the influence of temperature and loading speed of this material class. In this work, SMC which based on a novel hybrid resin system were examined under bending loads using a electric-dynamic test system to realize high-force dynamic-mechanical-thermal analysis. The examined SMC materials were either discontinuously (Dico) or continuously (Co) reinforced. In addition a hybrid continuous–discontinuous reinforcement was realized by stacking different SMC materials. The mechanical characterization aimed to investigate the influence of the reinforcement architecture and the effect of hybridization on the temperature- and frequency-dependent material properties. Glass transition temperature of the hybrid SMC was comparable to glass transition temperature of the discontinuous glass fiber reinforced component. Compared to the continuous carbon fiber SMC, the decrease of storage modulus of the hybrid SMC could be shifted to higher temperatures and damping was also significantly increased due to hybridization