Electromagnetic Properties Of Modern Aviation Composite Materials Research

The aeronautical composite materials are developing rapidly due to the wide spreading use of them on the new generation of civil aircraft which bring a lot of problems. The conductive performance of composite materials are poorer than the traditional metal materials, which means the experiment data from the test of metal materials cannot directly be used for the design or manufacture of the new aircraft. Therefore, it’s crucially important to make research on the electronic performance of composite materials.It is quite time-consuming and costly for the experimental research, which could extend the period of the manufacturing. The purpose of this paper is to investigate the shielding performance of the composite materials and the electromagnetic distribution when they are stroked by the lightning. We mainly discussed the following problems:(1) We studied the shielding effectiveness (SE) of the composite materials. And we analyzed the electromagnetic parameters of fiber composite materials with effective medium theory, deduced the formula of the reflection coefficient using the transmission line theory and calculated the reflection coefficient, transmission coefficient and shielding effectiveness of the materials with different parameters and designed the computer program. By comparing the results obtained from the equivalent method with finite-difference time domain (FDTD) results, we test the calculation precision of the program. Then we modified the parameters of the materials to observe the change of the SE, when the fiber period was small which means the Program is of high precision.The results show that the shielding effectiveness becomes better when the conductivity of the fiber is greater, or the diameter of the fiber is bigger, or the thickness of the materials is thicker. However, when we increase the permittivity of the medium, the shielding effectiveness becomes worse. And when we change the permittivity of the fiber, the shielding effectiveness remains unchanged.(2) We analyzed the electromagnetic distribution by applying3D finite-difference time domain approach when the aircraft cabin was stroked by the lightning. The cabin was a cube, the walls of which were realized by thin panels protected by conductive paint. Inside the cube there was a lightning rod which was simulated by a thin wire. We calculated the electromagnetic distribution of two different structures, and analyzed the impact on the lightning protection of the composite materials when the lightning rod existed.The results reveal that electric field around the wire inside the cube stroked by lightning is higher than which in other area. The peak of the electromagnetic field inside the cube is related to the wire. If the wire locates at the strike point, the peak increases significantly. It can be perceived that after the upper side of the cube is stroked by lightning, the current flows through the wire, and the current density of the area that we protected decreases obviously, so that we achieve the goal of lightning protection.