Study of phenomena occurring in the surface layer of glass and carbon fiber-reinforced plastics during machining

MINIATURA 6

Funding Organization: National Science Centre

Project title: Study of phenomena occurring in the surface layer of glass and carbon fiber-reinforced plastics during machining

Agreement number: DEC-2022/06/X/ST8/00572

Project implementation period: 01.10.2022 - 30.09.2023

Principal Investigator: dr inż. Krzysztof Ciecieląg

Project value: 46 838,00 PLN

Funds granted for Lublin University of Technology: 46 838,00 PLN

Abstract: Composite materials are widely used in the aerospace and automotive industries for the production of machines and structures. Polymer composites are used for responsible and loaded machine parts and devices. Due to an increasing demand for these materials, composites are subjected to machining processes. The method for manufacturing polymer composites has a significant impact on the properties of the obtained material and its production cost. Machining is applied to obtain the required shape and dimensional tolerance of a finished product. The processing of composite materials differs from that of metal and metal alloy due to the anisotropy and heterogeneity of the structure of these materials. An important factor in machining is the type of cutting tool. Polymer composites are difficult-to-machine materials that require the use of appropriate tools and machining conditions. Machining methods such as turning, drilling, milling and grinding are widely used to obtain surfaces and shapes that are impossible to achieve at the manufacturing stage. The machining of composite materials is primarily used for making and countersinking holes, complex shaped cuts, recesses, grooves and narrow channels, as well as for thread cutting, surface milling and many other operations. Cutting speed and feed must be properly selected to avoid delamination and overheating of the composite material. Composite materials differ depending on their fiber type and orientation, and matrix properties. Given a large number of factors influencing the machining process, it is therefore difficult to establish unambiguous relationships between individual input factors and machining effects.
Based on previous studies and a literature review, it was possible to determine the milling and drilling parameters which ensure the required accuracy and surface quality. Investigations of surface defects occurring during machining were also carried out. Results showed that the machining of polymer composites reinforced with glass fibers was characterized by lower cutting forces, and that the obtained surface was characterized by lower values of roughness and waviness parameters. However, it must remembered that this material is characterized by high strength parameters in relation to its specific weight. This research project will involve conducting experiments on polymer composites reinforced with glass and carbon fibers using specially dedicated tools with polycrystalline diamond (PCD) coating.The use of these tools will make it possible to optimize cutting processes while maintaining high surface quality. A comparative analysis of milling and drilling processes conducted with the use of different types of tools and cutting parameters will also be performed. In addition to that, surface structure geometry (roughness, waviness) will be assessed via microscopic examination. Obtained results will make it possible to determine the effect of variable cutting parameters on the surface roughness and waviness of the tested composite materials. Also, cutting forces and temperature during machining will be investigated in order to avoid tool damage and material overheating. Surface structure geometry and hardness will be evaluated after each machining process conducted with different cutting parameters. Preliminary simulations of processing polymer composites will also be performed in the ABAQUS program by the finite element method (FEM). Experimental research of polymer composites covers the area of the discipline of mechanical engineering.
Recent studies on milling and drilling describe the results of the research on parameters, tools, thermal conditions, fiber orientation on the cutting force and torque, surface quality (mainly roughness) of composite materials  and the effect of many other aspects on their machinability. However, given the heterogeneity and anisotropy of composite materials, it is difficult to unambiguously describe phenomena occurring in their surface layer after processing. This research project will make it possible to determine exactly the machinability of polymer composites. The preliminary research will make it possible to verify the adopted methodology as well as to specify further research directions. Results of the research conducted under this project will be published in a prestigious scientific journal with a high citation rate.