Mechanical Reinforcement and Warpage Mitigation of FGF 3D-Printed High-Density Polyethylene Composites by Incorporating Vinyl-Functionalized Carbon Fiber

High-density polyethylene (HDPE) composites face severe warpage in fused granular fabrication (FGF) 3D printing due to crystallization shrinkage and poor fiber-matrix compatibility. Herein, vinyl-functionalized carbon fiber (mCF) was prepared via desizing, oxidation, and silane grafting to reinforce HDPE/POE blends. The modification enhanced interfacial adhesion, reduced porosity, and promoted formation of a percolated filler network, as confirmed by SEM, FTIR, and rheology. Compared to raw CF composites, mCF systems exhibited higher storage modulus, lower tanδ , and improved stress transfer, leading to superior mechanical strength and thermal resistance. Notably, warpage was significantly suppressed at moderate loadings, while high mCF content caused viscosity-driven porosity increase. The 12.4 wt% mCF composite achieved balanced reinforcement and dimensional stability. This work demonstrates that interfacial engineering via silane coupling is an effective strategy to mitigate warpage and enhance performance of polyolefin-based 3D-printed components. Graphical Surface engineering reconstructs the carbon fiber/polyethylene interface, as confirmed by FTIR, TGA, and SEM analyses, resulting in enhanced interfacial adhesion and efficient stress transfer. The interconnected carbon-fiber framework provides a multiscale thermo-mechanical constraint that suppresses shrinkage-induced deformation, leading to outstanding dimensional stability, superior mechanical performance, and near-zero warpage in extrusion-based 3D printed polyethylene composites.