Advances in materials science and technology have led to the development of composites, one of the most cutting-edge and adaptable engineering materials. Composite materials are increasingly being used in a variety of scientific and technological domains because of their distinct mechanical and physical characteristics. Composites are composed of two or more materials with different chemical or physical characteristics. But when these materials are mixed, they create new, better materials with respect to strength, stiffness, corrosion resistance, fatigue resistance, fatigue life, thermal insulation, thermal conductivity, temperature-dependent behavior, and weight. Composites made of polymers provide better mechanical, physical, and thermal qualities. Consequently, these composites have improved throughout time as an alternative to traditional materials. Some of the top engineering colleges in Nashik offer dynamic programs to teach students about fiber reinforced composite.
A lengthy chain of repeating monomer units makes up polymer materials. The two forms of polymer matrices—thermoset resin and thermoplastic resin—are distinguished by their molecular structures. In contrast to thermoplastic resins, which may be recycled and molded, thermoset resins cannot. Compared to thermoplastic polymers, thermoset polymers exhibit superior strength and thermal stability. The need for composite materials has been rising in tandem with the engineering sector’s steady expansion. Particularly, because of its excellent mechanical properties, high strength-to-weight ratio, and resistance to corrosion, fiber- reinforced polymer (FRP) has emerged as a highly advanced composite material utilised in a variety of industries, including aerospace, automotive, construction, and marine.
The fundamental procedure for producing the required size and form with dimensional accuracy is machining. Compared to traditional materials, FRP is inhomogeneous and anisotropic, which gives it special machining properties. The relative volumes of the fiber and matrix materials, fiber orientation, and various fiber reinforcement and matrix qualities all affect how FRP composite laminates machines. The fiber is strong and brittle, whereas the matrix material is weak and just slightly ductile. Because of the differences in these materials’ properties and degree of anisotropy, it is difficult to forecast how they will behave during machining. The machinability of these composites has a major impact on their functional efficiency. Both conventional and unconventional methods can be used to machine FRP composites.
Conventional techniques of removing material with mechanical tools and equipment are referred to as conventional machining. To mold a workpiece into the required shape. These procedures entail direct contact between a cutting tool and the workpiece. Conventional machining includes operations including drilling, milling, turning, shaping, and grinding. These procedures are used to get the workpiece to the proper size and shape.
Drilling:
Drilling holes is necessary for the assembly and maintenance of structural components in a variety of manufacturing sectors, including the automotive and aerospace industries. For example, transport planes have many drilled holes. Most of these apply to riveted and bolted joints. A jet fighter requires approximately 300,000 holes, while a commercial aircraft requires 1.5 to 3 million holes. However, flaws in the drilled holes could put a lot of stress on the rivets and other parts, leading to an unexpected structure failure and potential financial or even fatalities. Because polymeric composites are anisotropic and inhomogeneous in comparison to conventional materials, drilling them is therefore a substantial challenge. Numerous components are rejected as a result of various forms of damage that occur in FRPs during drilling, including delamination, spalling, fiber breakage, and pull-out. Therefore, a deeper comprehension is needed to enhance these composites’ performance.
Milling:
A revolving cutting tool known as a milling cutter is used to remove material from a workpiece in order to generate shapes and features. This process is known as milling. The inhomogeneity of the material and the abrasiveness of its reinforcing make milling fiber-reinforced polymer (FRP) composites difficult. However, because to its accuracy, milling is a favored machining method.
Machining of FRP composites by traditional cutting tools is challenging and leads to poor machining quality. This is primarily due to anisotropy, inhomogeneous composition, and too much cutting force found on the cutting tool owing to thermal expansion. Moreover, fiber spalling and delamination in the machining edges considerably decrease the final part quality. The use of nonconventional as a sophisticated machining technique is growing in popularity. They work with a broad range of materials with fast production rates, shallow angle capabilities, quick hole size adjustments, and the ability to machine a variety of materials—including composites, high-strength materials, ceramics, etc.—all contribute to its appeal. Because there is no direct touch between the workpiece and the tool, unconventional machining techniques
fall within the non-contact process category. These procedures use an alternative energy source to eliminate extraneous material from a workpiece. The manufacturing industry uses a wide variety of non-traditional machining methods. These include: (i) Ultrasonic machining, (ii) Laser beam machining, (iii) Water jet machining, (iv) Abrasive water jet (AWJ) machining, (v) Chemical machining, (vi) Electrochemical machining, and (vii) Electro discharge machining (EDM).
Abrasive Water Jet Machining
In 1968, Dr. Norman C. Franz introduced the initial concept of water jet machining. The first commercial water jet was created in 1971 based on this concept. In 1980, Dr. Hashish came up with the idea of incorporating abrasives into water jets, and the AWJ machine was created to cut industrial materials. A pressure intensifier, nozzle positioning system, water capturing portion, abrasive feeding system, and mixing unit make up a typical AWJ machining system. It increases the rate of material removal and cutting speed by eroding hard materials and strong composites with a high-velocity jet of water and abrasive mixture through the nozzle. Erosive forces are the main objective of abrasive materials. Highly durable materials including sapphire, tungsten carbide, diamond, and others make up AWJ nozzles.
The catcher tank, which is positioned beneath the work material, collects scrap and water jets created during the machining process. Because AWJ machining is a non-electrical, non-thermal, and non- chemical process, it does not alter the physical or metallurgical characteristics of the work material. Numerous factors that determine the overall system’s quality and effectiveness are associated with AWJ machining of FRP composite. Aspects of the target material, abrasive properties, nozzle properties, hydraulic characteristics, and cutting parameters are examples of process parameters. Notwithstanding its many benefits, the AWJ method has many drawbacks when it comes to drilling FRP laminates, including surface qualities, kerf geometry, and delamination.
Laser Machining
Laser machining is a non-contact technique which does not include tool wear and mechanical cutting forces. LBM is a thermal method where removal of material occurs applying melting and vaporisation. In this process, a collimated beam is directed on a localised zone. The collimated laser beam assists in melting of the work material and the molten work material is taken away from the machining region with the help of a high velocity gas jet to produce a tidy edge. This technique is acquiring recognition owing to the non-contact machining with no tool wear, altered energy density, flexibility in range of parameters, minimum HAZ, easiness of automation and precise cuts and quick processing. The commonly used laser in industries based on requirement are fiber laser, CO2 laser and neodymium doped yttrium aluminium garnet (Nd: YAG) laser.
Conclusion
Machining of FRPs provides distinctive challenges owing to their heterogeneous and anisotropic properties. Defects like delamination, fiber pull-out, and tool wear are frequently caused by traditional machining techniques including drilling, milling, and turning. Although these processes are still frequently employed, their drawbacks have prompted the creation of unconventional approaches such as electrical discharge machining (EDM), water jet machining (WJM), and laser beam machining (LBM). These cutting-edge methods provide greater surface integrity, reduced heat damage, and increased precision.
In the end, the qualities of the composite material, the required tolerances, and the application requirements determine which machining technique is best. Pursuing an engineering program from one of the best engineering colleges in Maharashtra can help you understand this concept in-depth. Both conventional and nonconventional machining procedures for FRCs are becoming more effective and high- quality due to ongoing research and technical developments.