318 M. F. Amateau, B. Stutzman, J. C. Conway, J. Halloran Whisker-reinforced ceramics also exhibit Malakoff Industries Inc. The Sic whiskers were improved wear resistance compared to unrein- obtained from Advanced Composite Materials forced ceramics. The tribological characteristics of Corporation, Greenville Sc monolithic ceramics can be improved through the addition of wear resistant surface layers such as 3 LAMINATE DESIGN SiN. sialON, or TiC. In the current art of man facturing whisker-reinforced ceramic cutting Modified classical plate laminate theory was used tools, the matrix ceramic and the whiskers are to thermoelastically tailor the laminate design to pre-blended and hot pressed to form the densified optimize the residual stresses, toughness and the tool insert body. This method provides very little tribological performance. Thermoelastic properties control over the distribution and orientation of of lamina materials used for laminate properties the whisker reinforcements in the final tool body. calculations were obtained from manufacturer Another significant limitation to the current supplied data when available. For composites method of manufacturing of whisker-reinforced where such data were not available the lamina ceramic cutting tools is the cost of the silicon car- properties were calculated from constituent data bide whiskers. Whiskers cost 10 times that of the using the Halpin-Tsai method. 8.9 A summary of common matrix materials; hence, material designs lamina properties is given in Table 2 and manufacturing methods suitable for cost The designs used in this study are considered ffective cutting tools, are required. Manufactur- hybrid composites by conventional laminate ter ing method and material designs for ceramic cut- minology since they use multiple compositions ting tools, that make efficient use of the minimum within a single laminate. Some of the designs used amount of reinforcing whiskers to minimize cost, pure alumina surface layers to provide chemically are the ultimate goals of this research inert material on the rake face, while other designs used titanium carbide and silicon carbide rein 2 MATERIALS forcement alumina on this surface. The individual layers in all designs were arranged symmetrically Composites were fabricated using either Al2O, or with respect to the mid-plane to eliminate in-plane Si3N4 as the matrix with TiC particulate, TiN par- and out-of-plane coupling of stresses and deflec ticulate, or SiC whisker reinforcements. A list of tions. Laminate designs have been selected to these materials and their designation is given in avoid large tensile stresses within the lamina and Table 1. The osition amounts given in this large differences in stresses between lamina to table are in percent. The alumina powers, minimize delamination. All designs except GX-06 grade RC-HPBM containing 0-05% MgO, with a and GX-08 use compressive stresses on the outer article size of 34 um were obtained from surfaces Table 1. Materials used in this program Composition Designation Source 30SiCw-70 Al2O3 NG-300 Grccnlcaf Corporation 26TiCp-79Al2O HC-2 NTK Corporation 17TiNp-83S RD3905 Greenleaf Corporation 17TiNp-83Si3N NTK Corporation TiCp-Al203 5 layer laminate #1 Gx-06 Penn State University TiCp-Al2O3 5 layer laminate #2 GX-08 Penn State University TiCp-Al2O3 3 layer laminate GX-20 Penn State University SiCw-AL2O3 7 layer laminate Penn State University SiCw-AL2O3 5 layer laminate DX-13 Penn State University Table 2. Lamina properties used to calculate laminate properties Material Elastic modulus Poisson's ratio Shear modulus Coefficient of thermal (GPa) expansion(10/C) 159 792 5SiCw/95Alumina 160 10SiCw/90Alumina 772 20SiCw/80Alumin 165 26TiC/74Alumina 022318 M, F. Amateau, B. Stutzman, J. C. Conway, J. Halloran Whisker-reinforced ceramics also exhibit improved wear resistance compared to unrein￾forced ceramics. The tribological characteristics of monolithic ceramics can be improved through the addition of wear resistant surface layers such as S&N,, SiAlON, or TiC.7 In the current art of man￾ufacturing whisker-reinforced ceramic cutting tools, the matrix ceramic and the whiskers are pre-blended and hot pressed to form the densified tool insert body. This method provides very little control over the distribution and orientation of the whisker reinforcements in the final tool body. Another significant limitation to the current method of manufacturing of whisker-reinforced ceramic cutting tools is the cost of the silicon car￾bide whiskers. Whiskers cost 10 times that of the common matrix materials; hence, material designs and manufacturing methods suitable for cost effective cutting tools, are required. Manufactur￾ing method and material designs for ceramic cut￾ting tools, that make efficient use of the minimum amount of reinforcing whiskers to minimize cost, are the ultimate goals of this research. Malakoff Industries Inc. The SIC whiskers were obtained from Advanced Composite Materials Corporation, Greenville S.C. 3 LAMINATE DESIGN Modified classical plate laminate theory was used to thermoelastically tailor the laminate design to optimize the residual stresses, toughness and the tribological performance. Thermoelastic properties of lamina materials used for laminate properties calculations were obtained from manufacturer supplied data when available. For composites where such data were not available the lamina properties were calculated from constituent data using the Halpin-Tsai method.8,9 A summary of lamina properties is given in Table 2. 2 MATERIALS Composites were fabricated using either Al,O, or S&N, as the matrix with TiC particulate, TIN par￾ticulate, or SIC whisker reinforcements. A list of these materials and their designation is given in Table 1. The composition amounts given in this table are in volume percent. The alumina powers, grade RC-HPBM containing 0.05% MgO, with a particle size of 34 pm were obtained from The designs used in this study are considered hybrid composites by conventional laminate ter￾minology since they use multiple compositions within a single laminate. Some of the designs used pure alumina surface layers to provide chemically inert material on the rake face, while other designs used titanium carbide and silicon carbide rein￾forcement alumina on this surface. The individual layers in all designs were arranged symmetrically with respect to the mid-plane to eliminate in-plane and out-of-plane coupling of stresses and deflec￾tions. Laminate designs have been selected to avoid large tensile stresses within the lamina and large differences in stresses between lamina to minimize delamination. All designs except GX-06 and GX-08 use compressive stresses on the outer surfaces. Table 1. Materials used in this program Composition ~OSICW-70 AI,O, 26TiCp79Al,03 17TiNp-83Si3N, 17TiNp-83Si,N, TiCp-Al,O, 5 layer laminate #I TiCp-A&O, 5 layer laminate #2 TiCp-Al,O, 3 layer laminate SiCw-Al,O, 7 layer laminate SiCw-Al,O, 5 layer laminate Designation WG-300 HC-2 RD-3905 sx-5 GX-06 GX-08 GX-20 DX-14 DX-13 Source Greenleaf Corporation NTK Corporation Greenleaf Corporation NTK Corporation Penn State University Penn State University Penn State University Penn State University Penn State University Table 2. Lamina properties used to calculate laminate properties Material Alumina 5SiCw/95Alumina lOSiCw/90Alumina 20SiCw/80Alumina 26Ti074Alumina Elastic modulus (GPaI 390 392 395 400 395 Poisson’s ratio 0.23 0.23 0.22 0.22 0.22 Shear modulus Coefficient of thermal (GPaI expansion (lO?C) 159 7.92 160 7.72 161 7.54 165 7.16 162 8.10