A review of FDM methods, microstructure, and structure–property relationships in polymer composites

Fused Deposition Modeling (FDM) is one of the most widely used additive manufacturing processes for fabricating complex geometries from thermoplastic polymers. Despite its popularity, the technique faces limitations due to poor mechanical characteristics and inconsistent quality, restricting its large-scale industrial adoption. Over the past two decades, significant research has focused on incorporating composite reinforcements to overcome these challenges. Strengthening the polymer matrix with nanoparticles, short fibers, or continuous fibers has been shown to enhance mechanical, thermal, and electrical properties beyond those of the neat polymer. The performance of FDM-printed composites strongly depends on the quality of feedstock filaments and precise, error-free printing execution, making them critical to scalability. This review highlights advances in FDM-based materials tailored for industrial applications, including biomedical, tooling, construction, defense, automotive, electronics, and aerospace. Structural integrity, microstructural evolution, mechanical performance, and their correlation through modeling techniques are discussed in detail. Reported studies reveal similarities in microstructures and properties across various FDM composites, which are categorized here by reinforcement type and application. This review provides a unified framework that integrates material development, microstructural characterization, and predictive modeling to establish clear process–structure–property relationships in FDM-printed polymer composites, offering practical insights for their industrial application.