Análise comparativa das características térmicas, químicas e mecânicas do PLA impresso e sem reforço de fibra de carbono

Abstract

The advent of additive manufacturing techniques has revolutionized the production of components with intricate geometries or those challenging to fabricate using conventional manufacturing routes. A range of materials can be employed as raw materials in such processes. In the case of polymer utilization, literature has demonstrated that additively manufactured parts exhibit, on average, 85% of the mechanical strength of the same material processed through injection molding techniques. To meet design requirements, enhancing the mechanical, thermal, and electrical properties of additively manufactured polymer-based components can be achieved through the addition of reinforcing materials. In this context, the objective of this study was to evaluate the effect of adding carbon fiber on the thermal, chemical, and mechanical characteristics of samples produced through the Fused Filament Fabrication (FFF) 3D printing process using a commercial Poly(lactic acid) (PLA) filament reinforced with carbon fiber. For comparative purposes, samples and test specimens were also 3D printed using a regular commercial PLA filament from the same manufacturer and subjected to the same characterizations. Chemical characterization of the printed material was performed using Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, and X-ray Diffraction (XRD). Thermal characterization involved Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Finally, mechanical characterization employed uniaxial tensile tests, three-point bending, Single- Edge Notched Bending (SENB), impact, and hardness tests. Raman spectra of the carbon fiber-reinforced PLA samples revealed characteristic D and G bands, whereas FTIR spectra did not indicate chemical interactions between carbon fibers and the PLA matrix. XRD patterns revealed low crystallinity and low-intensity peaks associated with the filament pigment in both materials, with specific peaks related to crystalline PLA for the natural PLA and to the carbon fiber plane for the reinforced PLA. The DSC results showed a slight increase in the PLA melting and crystallization temperatures with the addition of carbon fibers. Conversely, TGA analysis revealed a reduction in the onset temperature of PLA's thermal decomposition with the presence of these fibers. In the tension, flexion, impact, and three-point bending tests on standard SENB samples, the addition of carbon fibers led to a reduction in both tensile and flexural strength, while increasing the values of the elastic modulus and deformation under tension and flexion. Furthermore, the impact energy required to fracture the PLA increased with the inclusion of these fibers. Hardness measurements indicated a 7% increase in PLA hardness. In summary, the findings suggest that incorporating carbon fibers may broaden the potential applications of PLA.