Infill Density Influence on Mechanical and Thermal Properties of Short Carbon Fiber-Reinforced Polyamide Composites Manufactured by FFF Process

Abstract

In three-dimensional (3D) printing, one of the main parameters influencing the properties of 3D-printed materials is the infill density (ID). This paper presents the influence of ID on the microstructure, mechanical, and thermal properties of carbon fiber-reinforced composites, commercially available, manufactured by the Fused Filament Fabrication (FFF) process. The samples were manufactured using FFF by varying the infill density (25%, 50%, 75%, and 100%) and were subjected to tensile tests, three-point bending, and thermal analyses by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). It was shown that the samples with 100% ID had the highest values of both tensile, 90.8 MPa, and flexural strengths, 114 MPa, while those with 25% ID had the lowest values of 56.4 MPa and 62.2 MPa, respectively. For samples with infill densities of 25% and 50%, the differences between the maximum tensile and flexural strengths were small; therefore, if the operating conditions of the components allow, a 25% infill density could be used instead of 50%. After DSC analysis, it was found that the variation in the ID percentage determined the change in the glass transition temperature from 49.6 °C, for the samples with 25% ID, to 32.9 °C, for those with 100% ID. TGA results showed that the samples with IDs of 75% and 100% recorded lower temperatures of onset degradation (approximately 344.75 °C) than those with infill densities of 25% and 50% (348.5 °C, and 349.6 °C, respectively).

Compression and Bending Properties of Short Carbon Fiber Reinforced Polymers Sandwich Structures Produced via Fused Filament Fabrication Process

“…The composite sandwich specimens were analyzed microscopically on the sections perpendicular to the XY plane (cross section) and according to the construction direction-Z axis (longitudinal section) with a magnification of 100×. On the microscopic analysis, typical defects of short fiber-reinforced composites were found, similar to the ones in other studies [7,23,30,[60][61][62]. The defects are rectangular and triangular voids formation, inter-layer voids, voids found in the matrix or filament, and poor adhesion between the fiber and the matrix.…”

Natural and Synthetic Polymer Fillers for Applications in 3D Printing—FDM Technology Area

“…Printed samples had higher stiffness values than the IM parts. The reinforcing effect was also confirmed for PA when 15% of short CFs had the highest values of both tensile, 90.8 MPa, and flexural strength, 114 MPa [194]. Furthermore, it was observed that the increase in the infill density determines the decrease in the glass transition temperature.…”

Comparing Degradation Mechanisms, Quality, and Energy Usage for Pellet- and Filament-Based Material Extrusion for Short Carbon Fiber-Reinforced Composites with Recycled Polymer Matrices

“…However, for the samples with sCF (entries 3-4 and 7-8), the FFF-processed samples demonstrated better thermal stability compared to DPAM by 3.4% and 30.6%. The significant influence of CF on the thermal stability of the material has been indicated in the literature and is dependent on the dispersion quality [57]. Hence, one could expect that a morphological analysis (next subsection) should reveal a more random CF incorporation for DPAM.…”