Machining of Composite Materials R. Teti University of Naples Federico l, Italy Abstract Machining of composite materials is difficult to carry out due to the anisotropic and non-homogeneous structure of composites and to the high abrasiveness of their reinforcing constituents. This typically results in damage eing introduced into the workpiece and in very rapid wear development in the cutting tool ventional achining processes such as turning, drilling or milling can be applied to composite materials, provided propel ol design and operating conditions are adopted verview of the various issues involved in the conventional achining of the main types of composite materials is presented in this paper Machining, Composite Materials, Conventional Cutting Processes ACKNOWLEDGEMENTS such as glass, graphite, boron, alumina and silicon Acknowledgements are due for papers, contributions and carbide, are highly abrasive and hard (sometimes as hard correspondence received from Messrs ("CIRP members) as or even harder than the tool material), conventiona Aspinwal, D K, University of Birmingham UK;"Balazinski machining is considered for composites because their M, Ecole Polytechnique de Montreal, Canada: *Byrne, G reinforcements are brittle and material separation is University College Dublin, Ireland; "Brinksmeier, E accomplished G deformation ahead of the tool. However, the cutting tool Naples Federico Il, Italy; *Chandrasekaran, H, Swedish materials must be attentively chosen to minimize wear due nstitute for metals Research. stockhol en: Chen to the hard abrasive constituents of the reinforcing phase J. Rotors Business Center. USA: 'Dornfeld. D in the composite representing the work material University of California, Berkeley, USA: *Geiger Machining of a composite depends on the properties and University of Erlangen-Nurnberg, Germany: Inasaki elative content of the reinforcement and Kentucky, USA; Klocke, F, Technical University of process. In addition, the choice of the spec Aachen, Germany: Komanduri, R, Oklahoma State depends upon the following factors type of machining peration, part geometry and size, finish and accul Japa-rsity, USA, *Narutaki, N, Hiroshima University, Japan:"Poll mann, W, Daimler Crysler AG, Stuttgart requirements, number of parts, diversity of parts(including Germany: Spur, G, Technical University Berlin the material of the parts), availability of appropria machine and cutting tools, availability of in-house Germany: Tomizuka, M, University of California, Berkeley technol USA: *Uhlmann, F,, Technical University Berlin, Germany ufacturing schedule, capital requirements and justification for new equipment, environmental and safety considerations, and Weig, E, HSC-Manufact. Engineering, Austria; "Weinert overall costs K, University of Dortmund, Germany; *Wertheim, R ISCAR Ltd. Israel 2 COMPOSITE MATERIALS PhD student Doriana D'Addona, University of Naples Federico I, Italy is gratefully thanked for her help and Composite materials are formed from two more support in the preparation of the text materials producing properties that could not be obtained from any one material. One of the constituent materials acts as the matrix and at least one other constituent material acts as the reinforcement in the composite Composite materials are used extensively as their higher of th specific properties(properties per unit weight) of strength to protect the reinforcement materials and stiffness, when compared to metals, offer interesting to distribute the stress to the reinforcement material(s) opportunities for new product design. However, being non to provide for the final shape of the composite part homogeneous, anisotropic and reinforced by very abrasive The role of the reinforcement material(s)is the following components, these materials are difficult to machine to provide the composite high mechanical properties Significant damage to the workpiece may be introduced to reinforce the matrix in preferential directions and high wear rates of the cutting tools are experienced The properties of a composite material depend on the Conventional machining practices, such as turning, drilling nature of the reinforcement and the matrix. the form of the and milling are widely applied to the machining of reinforcement(particles, fibres) and the relative content of composite materials in view of the availability of equipment reinforcement and matrix expressed as volume fraction and experience in conventional machining. Although some Vt=(reinforcement volume)composite volume)and vm of the materials used as reinforcement in composites (matrix volume) /(composite volume), where Vr+ VmMachining of Composite Materials R. Teti University of Naples Federico II, Italy Abstract Machining of composite materials is difficult to carry out due to the anisotropic and non-homogeneous structure of composites and to the high abrasiveness of their reinforcing constituents. This typically results in damage being introduced into the workpiece and in very rapid wear development in the cutting tool. Conventional machining processes such as turning, drilling or milling can be applied to composite materials, provided proper tool design and operating conditions are adopted. An overview of the various issues involved in the conventional machining of the main types of composite materials is presented in this paper. Keywords: Machining, Composite Materials, Conventional Cutting Processes ACKNOWLEDGEMENTS Acknowledgements are due for papers, contributions and correspondence received from Messrs (*CIRP members): Aspinwal, D.K., University of Birmingham UK; *Balazinski, M., Ecole Polytechnique de Montreal, Canada; *Byrne, G., University College Dublin, Ireland; *Brinksmeier, E., University of Bremen, Germany; Caprino, G., University of Naples Federico II, Italy; *Chandrasekaran, H., Swedish Institute for Metals Research, Stockholm, Sweden; Chen, L.J., Rotors Business Center, USA; *Dornfeld, D., University of California, Berkeley, USA; *Geiger, M., University of Erlangen-Nurnberg, Germany; *Inasaki, I., Keio University, Japan; *Jawahir, I.S., University of Kentucky, USA; *Klocke, F., Technical University of Aachen, Germany; *Komanduri, R., Oklahoma State University, USA; *Narutaki, N., Hiroshima University, Japan; *Pollmann, W., DaimlerCrysler AG, Stuttgart, Germany; *Spur, G., Technical University Berlin, Germany; Tomizuka, M., University of California, Berkeley, USA; *Uhlmann, F., Technical University Berlin, Germany; *Venkatesh, V.C., University of Technology Malaysia; *Weigl, E., HSC-Manufact. Engineering, Austria; *Weinert, K., University of Dortmund, Germany; *Wertheim, R., ISCAR Ltd., Israel. PhD student Doriana D'Addona, University of Naples Federico II, Italy, is gratefully thanked for her help and support in the preparation of the text. 1 INTRODUCTION Composite materials are used extensively as their higher specific properties (properties per unit weight) of strength and stiffness, when compared to metals, offer interesting opportunities for new product design. However, being non￾homogeneous, anisotropic and reinforced by very abrasive components, these materials are difficult to machine. Significant damage to the workpiece may be introduced and high wear rates of the cutting tools are experienced. Conventional machining practices, such as turning, drilling and milling, are widely applied to the machining of composite materials in view of the availability of equipment and experience in conventional machining. Although some of the materials used as reinforcement in composites, such as glass, graphite, boron, alumina and silicon carbide, are highly abrasive and hard (sometimes as hard as or even harder than the tool material), conventional machining is considered for composites because their reinforcements are brittle and material separation is accomplished by brittle fracture rather than plastic deformation ahead of the tool. However, the cutting tool materials must be attentively chosen to minimize wear due to the hard abrasive constituents of the reinforcing phase in the composite representing the work material. Machining of a composite depends on the properties and relative content of the reinforcement and the matrix materials as well as on its response to the machining process. In addition, the choice of the specific process depends upon the following factors: type of machining operation, part geometry and size, finish and accuracy requirements, number of parts, diversity of parts (including the material of the parts), availability of appropriate machine and cutting tools, availability of in-house technology, current machining practice, manufacturing schedule, capital requirements and justification for new equipment, environmental and safety considerations, and overall costs. 2 COMPOSITE MATERIALS Composite materials are formed from two or more materials producing properties that could not be obtained from any one material. One of the constituent materials acts as the matrix and at least one other constituent material acts as the reinforcement in the composite. The role of the matrix material comprises the following: - to protect the reinforcement materials; - to distribute the stress to the reinforcement material(s); - to provide for the final shape of the composite part. The role of the reinforcement material(s) is the following: - to provide the composite high mechanical properties; - to reinforce the matrix in preferential directions. The properties of a composite material depend on the nature of the reinforcement and the matrix, the form of the reinforcement (particles, fibres) and the relative content of reinforcement and matrix expressed as volume fraction: Vf = (reinforcement volume)/(composite volume) and Vm = (matrix volume)/(composite volume), where Vf+ Vm = 1