Carbon fiber sheet molding compounds (C-SMCs) are discontinuous fiber reinforced composite materials. Among them, epoxy-based C-SMCs are becoming relevant materials due to their high thermomechanical performance and better formability than continuous fiber reinforced composites. The thermomechanical performance of epoxy resins and epoxy based continuous carbon fiber composites have shown to be influenced by hygrothermal aging. In this work, this influence is studied for an epoxy-based C-SMC. Epoxy-based C-SMC samples were hygrothermally aged by means of accelerated conditioning, exposing them to 65% relative humidity, and 80 C in a climatic chamber. The equilibrium moisture content, as well as the moisture diffusion coefficient has been determined. The thermomechanical properties of epoxy C-SMC have been analyzed by dynamic mechanical analysis, tensile, 3-point bending, and short beam tests in dry and aged samples. The results showed that epoxy C-SMC is affected by hygrothermal aging in the cases of moisture intake and its effects on T g value, but interestingly, the hygrothermal aging did not generate any degradation effects in the mechanical response of epoxy C-SMC.
Sheet molding compounds (SMC) are ready-to-mold thermoset composite materials reinforced with discontinuous fibers, usually compression molded.Finite element (FE) based compression molding tools can be employed to optimize this process; FE tools require to define material models using raw material data measured through different characterization techniques. In this study, the cure kinetics of an epoxy-based carbon fiber SMC has been characterized by means of differential scanning calorimetry (DSC) and moving die rheometer (MDR) techniques. Based on these datasets, Claxton-Liska and Kamal-Souror models have been set and the compression molding of a validation plate was performed, both experimentally and virtually. The results indicate that, even if both characterization techniques are valid for SMC curing characterization, MDR technique enables the characterization of the material at real molding temperatures and the model based on MDR leads to more accurate results.
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