Development and characterization of milled carbon fiber-reinforced polypropylene filaments for fused deposition modeling: mechanical performance, moisture absorption, and morphological insights

Abstract This study explores the production, characterization, and performance evaluation of carbon fiber-reinforced polymer (CFRP) composite filaments designed for fused deposition modeling (FDM) applications. The primary objective was to investigate the influence of milled carbon fiber (MCF) content on the mechanical, moisture absorption, and morphological properties of polypropylene (PP)-based composites. Composite filaments were produced by blending micro-sized MCFs with PP granules, followed by a two-step extrusion process to create filaments with varying MCF contents (1–24 wt%). Test specimens were fabricated using 3D printing to evaluate the performance of the composite materials. The results demonstrated a significant enhancement in mechanical properties compared to neat PP. The composite with 9.09 wt% MCF achieved optimal performance, exhibiting increases in tensile and flexural strengths by 74% and 99%, respectively, relative to neat PP. However, higher MCF contents (16 and 24 wt%) led to reduced mechanical properties due to insufficient fiber-matrix adhesion, resulting in fiber pull-out. Moisture absorption studies revealed that the inclusion of MCFs increased the water uptake of the composites, with higher fiber concentrations correlating to greater moisture absorption. These findings underline the potential of MCF-reinforced PP composites for applications requiring improved mechanical performance, such as lightweight structural components. The study identifies an optimal fiber content of 9.09 wt% for maximizing strength while minimizing moisture-related trade-offs. Future efforts could focus on enhancing fiber-matrix bonding to improve performance at higher fiber concentrations.