**Acknowledgements**

abrasive in Cu matrix for machining CFRP. CFRP drilling tests were carried out with feed rate of 5 mm/min, peripheral wheel speed of 7000 rpm, spindle speed of 2800 rpm, and dry machining. Bidirectional CFRP composite laminates having thickness of 5 mm were used as workpiece material. Photographs of a hole having diameter of 20 mm drilled by the gyrodriving grinding wheel system equipped with fabricated Cu/diamond FGMs as a grinding wheel (Fig. 12a) and the one having diameter of 10 mm drilled by a conventional drill bit (Fig. 12b) in CFRP plates are shown in Figure 12. Delamination and burrs were seen in the drilled CFRP plate in the case of the conventional drill bit. It should be noted that precision drilling of CFRP plate without burring and delamination were achieved by the gyro-driving grinding wheel system equipped with fabricated Cu/diamond FGMs as grinding wheel. In this way, FGMs fabricated by the centrifugal sintered-casting method have been attempted to apply for

**Figure 12.** Drilled hole having diameter of 20 mm made by the gyro-driving grinding wheel system equipped with fabricated Cu/diamond FGMs as a grinding wheel (a) and the one having diameter of 10 mm made by a conventional

As the other possibilities for application of FGMs, materials for heat sink can be considered as candidate. Nowadays, thermal management materials such as heat sink for microelectronics and semiconductors have been investigated, extensively [27–30]. The materials currently used for heat sinks are Al and Cu due to their high thermal conductivity in metals and alloys. The thermal conductivities of Al and Cu are about 250 and 400 W m−1 K−1, respectively. On the other hand, diamond is well known as the material having the highest thermal conductivity in materials. To enhance the thermal conductivity of heat sink materials, Al/diamond and Cu/ diamond composites are promising materials. Our Al alloy/diamond and Cu/diamond FGMs fabricated by the centrifugal sintered-casting method might work as well in this field.

Two kinds of new processing routes for metal-matrix FGMs through combinations of powder metallurgy and casting were developed: the centrifugal mixed-powder method and the

the practical use.

44 Advances in Functionally Graded Materials and Structures

drill bit (b) in CFRP plates [17].

**4. Summary**

The authors would like to acknowledge financial supports by the Regional Innovation Cluster Program (Global Type) "Tokai Region Nanotechnology Manufacturing Cluster" from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. The au‐ thors would like to thank Mr. Hideaki Tsuge, Industrial Research Institute of Gifu Prefecture, for use of the gyro-driving grinding wheel system and his valuable inputs. The authors are grateful to Ms. Motoko Yamada, Nagoya Institute of Technology, for her assistance in parts of experiments.
