## 3 Results and Discussion
The method of using the mixture film rather than the direct application therefore can provide an improved damping capability through a better dispersion of particles. [PERSON] et al. insisted that when using PZT particles dispersed by hand, it was revealed that the optimal content exists according to particle dispersion, and through this, the importance of particle dispersion was confirmed [8]. In order to confirm the improvement in particle dispersion by the use of the film, the cross-section of the specimen was further investigated using EPMA. Lead (Pb) contained in the PZT particles was traced and mapped using the EPMA. As shown in Figure 6, good particle dispersion was confirmed. However, with the increase of the particle concentration, aggregations of the particles are formed, and the quality of dispersion deteriorates. Therefore, as described above, it is speculated that the cause of the decrease in loss factor for the particles loading at 25 g/m\({}^{2}\) is the deterioration in dispersion of particles in the film. SEM images of the cross-sections of the specimens are shown in Figure 7, which clearly shows aggregations and thus confirms that high particle concentration may be detrimental to the dispersion of particles. Figure 4: Loss factors of the CFRP specimens with PZT-particle-dispersed mixture films as functions of the frequency. Measurement data for different particle loadings. Figure 5: Loss factors of the specimens with PZT particle directly dispersed between the plies at 120 Hz. Comparison with the specimens with mixture films. Measurement data for different particle loadings. Figure 6: EPMA mapping images of lead (Pb) for evaluation of the dispersion of PZT in CFRP specimens. The blue dots show the degree of dispersion of the layer. The brighter the color, the stronger the signal from lead, which can be seen as large or clumped particles. Figure 8 shows the measured loss factors of the specimens interleaved with SMA-particle-dispersed mixture films as functions of frequency. Again, the amount of SMA particles in the mixture film varied from 0 g/m\({}^{2}\) to 25 g/m\({}^{2}\) with an increment of 5 g/m\({}^{2}\). As shown in Figure 8, the measured loss coefficient usually increases with the particle load. Unlike the PZT-particle-dispersed specimen, the loss factor value for the SMA-particle-dispersed specimen is higher than the neat specimen under all particle loading conditions. This difference is due to the different mechanisms of PZT and SMA on improving vibration damping within the composite material. In the case of PZT, dispersion inside the composite materials is very important because each electrical circuit should be connected through contact with carbon fiber to convert vibration energy into heat energy. In the case of SMA, the dispersion inside the composite material is less critical because it has vibration damping characteristics on its own due to its hyper-elastic property. In contrast to the specimens with PZT-particle-dispersed mixture films, for SMA interleaved specimens, the frequency range where the loss factor increases most were lower at approximately 50 Hz to 100 Hz. A closer look at the results of Figure 8 shows that the highest loss factor value was measured in a specimen containing 20 g/m\({}^{2}\) particles overall. The DMA results of the carbon fiber composite material including mixed PZT and SMA-particle-dispersed mixture film (PZT + SMA) are shown in Figure 9. The partial content of each kind of particles in the mixture film is 10 g/m\({}^{2}\) each to make the total particle content of the film 20 g/m\({}^{2}\). In the figure, the loss factor values of PZT + SMA dispersed specimens are compared with those of PZT dispersed and SMA dispersed specimens. As  
Figure 8: Loss factors (tan \(\delta\)) of CFRP specimens with SMA-particle-dispersed mixture film as functions of the frequency. Measurement data for different particle loadings. Figure 7: SEM images of fracture surfaces of the CFRP specimens with PZT specimens with different particle loadings.