The effect of reinforcement aspect ratio on the performance of PA66 composites with recycled carbon fiber and upcycled graphene nanoplatelets: An interface characterization from process to modeling

The use of recycled reinforcements in structural applications is growing due to concerns about the environmental impact and economic costs associated with energy-intensive production techniques of virgin fibers. However, limited research has explored the integration of multiscale reinforcements with different aspect ratios into PA66 composites to enhance their performance. In this study, the effect of reinforcement aspect ratio on PA66 composites by incorporating recycled carbon fibers and waste tire-derived graphene nanoplatelets (GNP) with oxygen surface functional groups is investigated. The objective of this work is to improve mechanical properties of the composites by promoting nucleation and enhancing the fiber/matrix interface. Through high shear mixing, recycled carbon fibers and GNP are effectively dispersed within the PA66 matrix. The alignment of these reinforcements during the injection molding process is monitored using the developed flow model, coupled with experimental rheological data. The resulting composites demonstrate significant improvements in mechanical properties due to enhanced interfacial interactions, including improved tensile properties up to 94%, flexural properties up to 86% compared to the neat PA66 by successfully integrating waste tire-driven GNP and recycled carbon fibers. This study contributes to the development of sustainable materials for load-bearing applications, utilizing recycled reinforcements with different aspect ratios.