Contribuição na retificação plana de compósito reforçado com fibras naturais com diferentes rebolos

Abstract

Composites materials in general combine in just one material properties that are not usually found in metallic materials, such as steel, for example, such as good mechanical and corrosion resistance or stiffness and fracture toughness combined with low density. For this reason, these materials have been used as raw materials in various engineering applications that were previously exclusive to steels and which require improved finishing. For these applications, grinding becomes one of the main alternatives as it allows obtaining combination of narrow dimensional and geometric tolerances, especially low roughness values (≤ 1.6 m). However, there are still few studies on the grindability of composites, for instance, about grinding data that can help in the selection of grinding wheels. In this sense, this work aims to contribute to the study of grinding of composites reinforced with natural vegetable fibers and to allow machining users to have a reference to take decisions. The workpiece material was an epoxy matrix composite reinforced with ramie natural vegetable fiber. 12 different tests were carried out by varying the type of grinding wheel (aluminum oxide and silicon carbide), cutting parameters: radial depth of cut (ae) of 15, 25 and 45 μm and the workspeed (Vw) of 2.7 and 7.5 m/min. The output variables investigated were the roughness and texture of the workpiece analyzed via optical microscope images as well as the workpiece surface hardness. The results showed that the roughness increased with the workspeed, unlike what is generally observed when grinding steels, for example, under the same cutting conditions. The lowest roughness values were obtained after employing the combination between an intermediate radial depth of cut of 25 μm at the lowest workspeed value of 2.7 m/min. As for the grinding wheel, silicon carbide outperformed alumina one when grinding composites reinforced with rami vegetable fiber due to the lower roughness values generated. In relation to Shore D hardness of the workpiece, no significant influence cutting parameters was observed on that.