## 6 Comparison of Shielding Ability According to the Structure of Composite Materials  
In this study, three types of composite materials were set and the radiation shielding efficiency was compared. By varying the layer thickness in the layered composite material, the fiber diameter in the fibrous composite material, and the particle diameter in the particulate composite material, the interface of the composite material was increased to induce a structural change inside the composite material. The linear attenuation coefficients of layered composites and fibrous composites have been investigated, and if there is a difference in the linear attenuation coefficients, it can be expected that the difference is due to the structure of the composite, not the difference due to the material. In order to compare the gamma-ray shielding ability by the structure of the composite material, the increase rate of the linear attenuation coefficient when the interlayer thickness of the layered composite material and the diameter of the fiber in the fibrous composite material became about 1/2 are graphed in Figures 14-16. As confirmed in the previous results, the increase rate of the linear attenuation coefficient due to the internal structure of the composite containing the fibrous composite and the particulate additive was greater than that of the layered composite, and the particle-added composite showed the largest increase. The linear attenuation coefficient increase rate of the layered composite is less than 10% under all conditions, and it is judged that the gamma-ray attenuation effect due to the layered structure is very small compared to other structures. In other words, it can be said that the attenuation effect due to scattering and refraction of gamma rays is large in the composite material of the other two structures compared to the layered composite material. Considering this, it is judged that it is possible to improve the shielding ability of the shielding material due to the change in the shape of the additive even if the type of material does not change. The attenuation effect of gamma rays is expected to be relatively large. Figure 12: Linear attenuation coefficient of fibrous composite; fiber diameter 0.1128 cm. Figure 13: Linear attenuation coefficient of fibrous composite; fiber diameter 0.1457 cm. In spite of the attenuation effect of gamma rays according to the composite structure, when the linear attenuation coefficients of the three composites are compared, the linear attenuation coefficients of the particle-added composites are mostly small, and when the gamma-ray energy is 0.1 MeV, in the case of the PE/tungsten composites, the layered composites It can be seen that the linear attenuation coefficient of has the highest value with a large difference (Figures 17-19). The purpose of this study is to examine the shielding effect caused by the composite structure, not the shielding effect of the radiation shielding composite. However, since the effect of the composite structure cannot be reflected only by simulation modeling, the internal interface of the composite material has been increased by modeling with a layered, fibrous, and granular structure composite material. From this point of view, the structure of the composite was changed by varying the layer thickness  
Figure 16: Rate of increase of linear attenuation coefficient caused by structural change of PE/tungsten composite. Figure 14: Rate of increase of linear attenuation coefficient caused by structural change of PE/copper composite. Figure 15: Rate of increase of linear attenuation coefficient caused by structural change of PE/lead composite. for the layered composite, the fiber diameter for the fibrous composite, and the particle diameter for the particle-added composite. In addition, by comparing the linear attenuation coefficients of each, the shielding performance according to the structural complexity was analyzed. This result is analyzed to be due to the problem of the designed composite material structure.