Reducing Warpage of Carbon Fiber Reinforced Polypropylene for Fused Filament Fabrication: The Role of Matrix Type and Composite Composition

Fused filament fabrication (FFF) of carbon fiber (CF) reinforced polypropylene (PP) is restricted by severe warpage and mechanical anisotropy, where matrix type and composite composition play the key role. This study systematically investigated three polypropylene (PP) matrices: high melt strength polypropylene (PPM), homopolymer polypropylene (PPH), and random copolymer polypropylene (PPR) with different CF loadings. The selected PPR composites were modified with maleic anhydride‐grafted polyolefin elastomer (POE‐g‐MAH) to achieve further compatibility. Characterizations like thermogravimetric analysis, crystallinity, rheological properties, porosity, mechanical properties, and scanning electron microscopy were conducted to clarify the trade‐off between CF network constraint and crystallization shrinkage. Results showed PPR had optimal printability and the lowest warpage compared to PPM and PPH. CF improved the stiffness of printed samples but increased anisotropy; POE‐g‐MAH enhanced interfacial bonding, reduced porosity, and balanced strength‐toughness. The sample PPR‐POE‐2CF achieved 91.1% higher X ‐direction tensile strength, 107.2% better notched impact toughness, and 64.1% lower warpage than Neat PPR, with a porosity of 0.037. This work provides a practical and scalable strategy for high‐performance PP/CF filaments available for FFF.