Polymer nanocomposites has become one of the frontiers of materials sciences since the 1990s. It is found that the addition of nanoparticles, such as nanoclays or carbon nanofibers, into polymer matrix can improve the strength and modulus, enhance the thermal stability, and lower the water absorption rate [1-5]. For example, it was reported that the strength and electric conductivity of the nano-powder of copper were much higher than bulk copper [6]. Scientists attributed this change to the nano-effects of the nanoparticles. It was predicted that the nanostructured composites might show a great difference from the conventional composites. Therefore, nanocomposites have attracted great interests in the recent 20 years.