This study is focused on the design of the composite stealth structures, which are divided into two parts such as the low-observable radome with the hybrid composite in part I and the radar absorbing structure (RAS) with the nano-composite in part II.
For the high performance radome structures in part I, high strength fibers such as glass and aramid fibers have been employed as the reinforcement for the faces of the sandwich construction and epoxy resin was used for the matrix of faces. For the core material, the polymeric foams such as polyvinyl chloride (PVC) and polymethacrylimide (PMI) foams have been selected. The mechanical and dielectric properties of the fiber reinforced composites and the polymeric foams were investigated for the application of the EM wave environmental conditions. Then, the hybrid composites such as the E-glass/aramid/epoxy hybrid composites were designed using the measured material properties. The objective of the hybrid composite for the low-observable radome was to exploit the advantages of each composite. Three design methods have been developed for the E-glass/aramid/epoxy hybrid composites: the characteristic medium thickness, the wavenumber and the dielectric wavelength methods. From the points of EM wave transmission characteristics, the dielectric wavelength method showed the best results to design the E-glass/aramid/epoxy hybrid composite for the low-observable radome. Then, the hybrid composite low-observable radomes composed of the E-glass/aramid/epoxy hybrid composite faces were designed. The EM wave transmission performances were evaluated with the numerical simulation and verified with the measurement. The mechanical performances were measured by the bending test and compared to those of the conventional low-observable radomes.
For the high performance RAS in part II, the material properties of the carbonaceous nano conductive particles such as the carbon black (CB), the carbon nanotubes (CNTs) and the graphene nanoplatelet have been surveyed for the additives of the E-glass/epoxy nano composite because they can improve the dielectric properties with small amount of concentration. Then, the E-glass/epoxy nano-composites for the RAS were fabricated and their dielectric properties were measured with respect to the weight percent of the CB, the CNTs and the graphene nanoplatelet. The equations for dielectric properties were derived in polynomial form using the dielectric properties of the E-glass/epoxy nano-composites measured by the free space measurement method.
Then, the theoretical study on the design of the RAS with the nano-composite was performed. An optimum design method for the nano-composite RAS based on the theoretical investigation was developed considering the effect of the dielectric property of the nano-composite. Also, the EM wave absorption mechanisms were studied, from which the design method for the nano-composite sandwich RAS was developed with the destructive interference condition of the EM wave. Using the optimum design method, the nano-composite RAS was designed and fabricated with respect to the carbonaceous nano conductive particles. Also, the nano-composite sandwich RAS was developed under the destructive interference condition method at the target absorbing frequencies of 9 GHz, 10 GHz, and 11 GHz. The EM wave absorbing performances of the nano-composite RAS and the nano-composite sandwich RAS were simulated with the 3-D numerical software and compared to the measured ones with the free space measurement. Finally, the mechanical performances of the nano-composite RAS and the nano-composite sandwich RAS were measured with the tension and the bending tests, respectively.
This study is focused on the design of the composite stealth structures, which are divided into two parts such as the low-observable radome with the hybrid composite in part I and the radar absorbing structure (RAS) with the nano-composite in part II.
For the high performance radome structures in part I, high strength fibers such as glass and aramid fibers have been employed as the reinforcement for the faces of the sandwich construction and epoxy resin was used for the matrix of faces. For the core material, the polymeric foams such as polyvinyl chloride (PVC) and polymethacrylimide (PMI) foams have been selected. The mechanical and dielectric properties of the fiber reinforced composites and the polymeric foams were investigated for the application of the EM wave environmental conditions. Then, the hybrid composites such as the E-glass/aramid/epoxy hybrid composites were designed using the measured material properties. The objective of the hybrid composite for the low-observable radome was to exploit the advantages of each composite. Three design methods have been developed for the E-glass/aramid/epoxy hybrid composites: the characteristic medium thickness, the wavenumber and the dielectric wavelength methods. From the points of EM wave transmission characteristics, the dielectric wavelength method showed the best results to design the E-glass/aramid/epoxy hybrid composite for the low-observable radome. Then, the hybrid composite low-observable radomes composed of the E-glass/aramid/epoxy hybrid composite faces were designed. The EM wave transmission performances were evaluated with the numerical simulation and verified with the measurement. The mechanical performances were measured by the bending test and compared to those of the conventional low-observable radomes.
For the high performance RAS in part II, the material properties of the carbonaceous nano conductive particles such as the carbon black (CB), the carbon nanotubes (CNTs) and the graphene nanoplatelet have been surveyed for the additives of the E-glass/epoxy nano composite because they can improve the dielectric properties with small amount of concentration. Then, the E-glass/epoxy nano-composites for the RAS were fabricated and their dielectric properties were measured with respect to the weight percent of the CB, the CNTs and the graphene nanoplatelet. The equations for dielectric properties were derived in polynomial form using the dielectric properties of the E-glass/epoxy nano-composites measured by the free space measurement method.
Then, the theoretical study on the design of the RAS with the nano-composite was performed. An optimum design method for the nano-composite RAS based on the theoretical investigation was developed considering the effect of the dielectric property of the nano-composite. Also, the EM wave absorption mechanisms were studied, from which the design method for the nano-composite sandwich RAS was developed with the destructive interference condition of the EM wave. Using the optimum design method, the nano-composite RAS was designed and fabricated with respect to the carbonaceous nano conductive particles. Also, the nano-composite sandwich RAS was developed under the destructive interference condition method at the target absorbing frequencies of 9 GHz, 10 GHz, and 11 GHz. The EM wave absorbing performances of the nano-composite RAS and the nano-composite sandwich RAS were simulated with the 3-D numerical software and compared to the measured ones with the free space measurement. Finally, the mechanical performances of the nano-composite RAS and the nano-composite sandwich RAS were measured with the tension and the bending tests, respectively.
