Avanços na manufatura híbrida de compósitos de matriz polimérica reforçados com fibra de carbono fragmentada

Abstract

The present work discusses Hybrid Manufacturing (MH) of polymeric composites of lactic acid polymer (PLA) with fragmented carbon fiber reinforcement. This topic was chosen due to the increasing demand for components with lower environmental impact, narrower geometric and dimensional tolerances, and higher geometric complexity in different scales, which motivated the development and research of modern technologies. In this context, biodegradable polymers, originated from renewable and biocompatible sources, present a promising perspective for biomedical, aeronautic, and automotive applications. As their use or reinforcement can be performed in conjunction with fragmented carbon fibers, addition is commonly associated with modification of thermal and mechanical properties. Meanwhile, the application of additive manufacturing (MA) presents itself as a possible solution for customizable components and with elevated geometric complexity, being Fused Filament Fabrication (FFF) one of the most used techniques. However, the application of this manufacturing technology has limitations, especially in dimensional and geometric tolerances. As opposed to MA, external cylindrical turning, a technique from the group of Subtractive Manufacture (MS), is able to obtain narrower tolerances, but with significant limitations in design freedom. These opposite characteristics can be combined in a hybrid context, amplifying the advantages and reducing limitations, but their association must be done considering the various control parameters of each technique. Thus, in accordance with the exposed, the present work is presented, which aims to optimize the dimensional and geometric characteristics by changing the control parameters of the additive and subtractive processes. In which the layer height, printing temperature and build plate temperature parameters of the MA were modified, while for MS were evaluated the cutting speed, feed rate and cutting depth. The tolerances were determined by a micrometer, as well as macrogeometric and microgeometric deviations through cylindricity and roughness deviations, respectively. Finally, it was possible to observe a significant reduction in tolerances and geometric deviations after application of the MS, in addition to the unique reduction in the application of the depth of cut in values proportional to raster width. Allied to the surface improvements, it was observed that the application of the MS and after the MA, when compared to the optimization by MA alone, presents lower manufacturing time. However, it was found that applying subtractive techniques after polymer extrusion still has limitations, the main one being the difficulty in ensuring the desired depth of cut during turning of parts with high cylindricity deviation, an attribute unfortunately characteristic of parts manufactured by FFF.