Electromagnetic shielding in avionic systems and development of a carbon fiber composite material for aircrafts

Increasing competition in aeronaustics and defence industry requires that materials used in aircrafts have both electromagnetic interference (EMI) shielding and excellent mechanical properties. In order to improve performances of airplanes, it is also important that they are designed with light materials. Therefore, in terms of electromagnetic shielding, it is a current topic that efficient composite materials are developed by using light reinforcement materials with excellent mechanical properties like carbon fiber. In this thesis, it was aimed that a carbon fiber composite material, which decreases negative impacts in avionics of electromagnetic waves was developed. In the experimental study performed, epoxy resin as the matrix material and unidirectional and bidirectional carbon fiber fabrics were used as the reinforcement material. Bidirectional glass fibre fabrics were also reinforced to get a higher breaking point and more flexibility in some composites manufactured. A total of eight composite laminates were manufactured as two sets in different orientations and number of plies by hand lay-up method. Carbon fiber volume fractions of the first and second set materials are in the ranges of 0.45-0.50 and 0.35-0.40, respectively. Composite materials that provide good values of shielding were determined by analyzing electromagnetic wave shielding characteristics for parameters like orientation angle, number of plies and fiber fabric type of the composite laminates. Electromagnetic shielding effectiveness (EMSE) values of the materials were measured in the frequency range between 900 and 6000 MHz, using Aaronia DFG 4060 wave generator, HF 60105 spectrum analyzer and two directional antenna. In the proposed frequency range, EMSE up to 62.13 dB was achieved. This value is accepted in the literature as a good level of shielding. Moreover, according to measurement results, it was concluded that EMSE was very higher when the orientation angle of the carbon fiber was 90°, as compared to 0°. Another parameter that affects EMSE is whether the carbon fiber fabric used is unidirectional or bidirectional because it was observed that the bidirectional fabric increased EMSE. In addition, it has been determined that the number of plies has less effect on EMSE than the orientation angle. In simulation part, EMSE was observed calculating electric field strengths for aluminium, iron, FR-4 and carbon fiber composite material by COMSOL Multiphysics software. Finally, in simulations carried out with F-16, F-22 and F-117 airplane models, it was shown that carbon fiber could utilized in aircrafts in terms of stealth technology.