## 5 Linear Attenuation Factor of Fibrous Composites
In the graph of the fiber diameter and the linear attenuation coefficient, when each graph in which the material and energy used for the composite are different is expressed as a linear function, the constant value corresponding to the slope and the y-intercept is the difference in the linear attenuation coefficient of the two materials composing the composite. is shown as a graph for Figure 9.  
Figure 7: Linear attenuation coefficient of fibrous composite; (**a**) PE/concrete, (**b**) PE/copper, (**c**) PE/lead, (**d**) PE/tungsten. The slope value was followed very similarly to the equation with a curved graph, and the equation is as follows. \[m\ =\ \frac{-177.16}{1+exp\Big{(}-\frac{\mu_{dif}-33.37}{7.93}\Big{)}} \tag{9}\]  
(\(m\) = slope of fibrous diameter vs linear attenuation coefficient graph; \(\mu_{dif}\) = difference in the linear attenuation coefficient of the two materials constituting the composite.) The constant value can be expressed as a graph in the form of a straight line, and the formula is as follows. \[C\ =\ 0.457\mu_{dif}+1.405 \tag{10}\]  
(\(C=y-\) intercept of fibrous diameter vs. linear attenuation coefficient graph.) Through Equations (9) and (10) derived above, it is thought that the linear attenuation coefficient of the composite material different from the diameter of the fiber can be predicted only with the linear attenuation coefficient of the two materials used for the fibrous composite. This is expected to be helpful when designing composite materials for radiation shielding in the future. Figures 10-13 show the linear attenuation coefficient of the fibrous composite material according to the gamma-ray energy. Previously, Figure 5 shows that the attenuation coefficient of the five materials used for modeling (concrete, PE, copper, lead, and tungsten) decreases as the radiation energy increases. However, Figures 10-13 show the attenuation coefficient according to the radiation energy of PE (matrix) and inorganic material (fiber)  
Figure 8: Cross section of thin film type fibrous composites. (**a**) d = 0.1784 cm, (**b**) d = 0.0461 cm. Figure 9: y-intercept(C) of graph for fiber diameter and linear attenuation coefficient. composites. These graphs are data to investigate the effect of the 'difference in the attenuation coefficient of materials' on the 'decrease in the attenuation coefficient according to the increase in radiation energy' for four composites made of different materials through the difference in the linear attenuation coefficient (difference in linear damping coefficient between two materials: PE/concrete < PE/copper < PE/lead < PE/tungsten). To compare the linear attenuation coefficients of 0.1 MeV and 10.0 MeV, the composite material with the largest difference was PE/tungsten with a fiber diameter of 0.0461 cm, and the difference became smaller as the diameter of the fiber increased. From this, it was confirmed that the larger the \(\mu_{diff}\) value, the greater the effect of the fiber diameter, that is, the structure. When the thickness of the layer was reduced in the layered composite and the diameter of the fiber in the fibrous composite was decreased, the increase in the shielding efficiency of the fibrous composite was larger than that of the layered composite as the internal interface area of the two composites increased. In the case of a layered composite, the angle between the incident radiation and the internal interface of the composite is 90\({}^{\circ}\), so it is considered that this is due to the amount of refraction of the radiation generated at the interface between the two materials is very small. It can be concluded that the attenuation is larger as the addition, it was confirmed that the greater the difference in the linear attenuation coefficient between the fibrous material and the matrix material, the greater the attenuation due to gamma ray scattering at the interface between the two materials. Figure 11: Linear attenuation coefficient of fibrous composite; fiber diameter 0.0798 cm.