## 3 Results and Discussion  
Figure 3 shows SEM images of the particle-dispersed epoxy film. The amount of dispersed PZT and SMA particles in the specimens were 20 g/m\({}^{2}\). For the specimen in which both PZT and SMA particles were mixed together, each particle contains 10 g/m\({}^{2}\) to make the total amount of particles in the specimen also 20 g/m\({}^{2}\). As can be seen, both PZT and SMA particles are uniformly distributed in the films. As the SMA particles have a smaller diameter than the PZT particles, the number of particles per unit area is larger for the SMA sample. However, as the densities of the two types of particles are similar, their  
Figure 1: Illustration of the cross-section of the CFRP specimen interleaved with the particle-dispersed mixture film. Figure 2: The Specim preparation and experiment scheme with photos. masses per unit area are almost identical. The film specimen with a thickness of 20 \(\upmu\)m was made with almost no void. It is noted that the films were casted on the substrate film by passing between two counter-rotating rollers with a gap of 20 \(\upmu\)m. Therefore, better dispersion of the particles may be expected with thinner films with the thickness close to the particle diameter. Considering the voids and dispersion of the particles, the best performance was expected for the film with a thickness of 20 \(\upmu\)m and all subsequent experiments were performed using 20 \(\upmu\)m thickness mixture films. Figure 4 shows the measured loss factors of the specimens interleaved with PZT-particle-dispersed mixture films as functions of frequency. As stated earlier, the amount of dispersed PZT particles in the mixture film was varied from 0 g/m\({}^{2}\) to 25 g/m\({}^{2}\) with an increment of 5 g/m\({}^{2}\). The specimen denoted as \"neat\" was not interleaved with mixture films and served as a reference. As can be seen from Figure 4, in general, the measured loss factor increases with the particle loading. For the PZT interleaved specimens, the frequency range where the loss factor increases most is approximately between 100 Hz and 150 Hz. The maximum loss factor peak was observed at 15 g/m\({}^{2}\) loading, and an improvement in loss factor can be observed up to 20 g/m\({}^{2}\) loading. In the case of 25 g/m\({}^{2}\), the loss factor shows almost no enhancement over neat specimens. It is presumed that, in the case of 25 g/m\({}^{2}\) loading film, the particle content was too high to make a film in which particles were uniformly dispersed. Figure 3: SEM images of the (**a**) PZT-, (**b**) SMA- and (**c**) PZT + SMA-particle-dispersed mixture films. Figure 5 shows the loss factors of the CFRP samples with PZT particles directly dispersed with between the composite plies at 120 Hz frequency. In previous research, a study was conducted through a specimen of composite materials in which PZT particles were directly dispersed. Existing results show that loss factor values are maximized at 120 Hz for specimens with direct distribution of PZT particles [25]. In this study, it was confirmed that the loss factor for different particle loadings was maximized in the range between 100 Hz and 150 Hz in a specimen using film-dispersed particles. However, in order to confirm the effect of particle dispersion on the loss factor through film dispersed particles, 120 Hz, which can confirm the most maximized effect by directly spraying particles, was compared. In the case of film-interleaved specimens with particle contents of 5 g/m\({}^{2}\) to 20 g/m\({}^{2}\), the loss factor values are higher than those of directly dispersed specimens by up to two times or more. For the directly dispersed specimens, the improvement in the loss factors was observed up to the particle loading value of 15 g/m\({}^{2}\). For higher particle loadings, the loss factor decreased due to poor dispersion of particles. On the other hand, when the mixture film was used, an improvement in the loss factor could be observed up to 20 g/m\({}^{2}\).