Morphological design of nano-engineered expanded graphite for enhanced dynamic energy absorption in liquid thermoplastic/CF composites

Graphene and related materials (GRMs) offer promising routes to enhance energy absorption in composites. This study investigates the morphological influence of two expanded graphite (EG) types i.e. nano-engineered worm-like EG (EG-W), and compact EG (EG-C) on microstructure, low-velocity impact, and thermomechanical performance used within recyclable liquid thermoplastic (Elium®) and carbon fiber composites (CF/Elium®). SEM, Raman, and XPS analyses reveal that EG-W’s higher aspect ratio, interconnected morphology, and balanced surface chemistry provide superior dispersion and load-transfer capability compared to EG-C, despite the latter’s higher oxygen functional content. Raman spectroscopy and 2D mapping further confirm notable differences in defect density, exfoliation, and spatial distribution across filler loadings (0–1.5 wt%). EG-W exhibits lower structural disorder (I_D/I_G=0.06) and improved exfoliation (I_2D/I_D=9.1), promoting uniform integration into the polymer matrix. Low-velocity impact tests (5–20 J) demonstrates that an optimal loading of 0.5 wt%, EG-W enhances peak force and energy absorption by 16.6 % and 18.9 %, respectively, compared to EG-C. At higher loadings (1–1.5 wt%), both systems exhibit reduced performance due to nanoparticle agglomeration. These findings highlight the critical role of EG morphology and concentration in tailoring impact resistance, enabling design of advanced recyclable composites for high-performance structural applications.