Influence of the Carbon Fiber Length Distribution in Polymer Matrix Composites for Large Format Additive Manufacturing via Fused Granular Fabrication.

Many studies assess the suitability of fiber-reinforced polymer composites in additive manufacturing. However, the influence of the fiber length distribution on the mechanical and functional properties of printed parts using these technologies has not been addressed so far. Hence, in this work we compare different composites based on Acrylonitrile Styrene Acrylate (ASA) and carbon fiber (CF) suitable for large format additive manufacturing (LFAM) technologies based on fused granular fabrication (FGF). We study in detail the influence of the CF size on the processing and final properties of these materials. Better reinforcements were achieved with longer CF, reaching Young's modulus and tensile strength values of 7500 MPa and 75 MPa, respectively, for printed specimens. However, the longer CF also worsened the interlayer adhesion of ASA to a greater extent. The composites also exhibited electrical properties characteristic of electrostatic dissipative (ESD) materials (10-10 Ω/sq) and low coefficients of thermal expansion below 15 µm/m·°C. These properties are governed by the CF length distribution, so this variable may be used to tune these values. These composites are promising candidates for the design of elements with enhanced mechanical and functional properties for ESD protection elements or molds, so the products can be manufactured on demand.