Integrated Design Of Low Detectable Structure Of Aircraft Wing

Low observability is one of the most important factors for evaluating defense penetration ability and survivability of military air vehicle. A highly potential method of improving the low observability is to apply low detectable(LD) structures. As a multi-functional structure, LD structure is able to meet the requirements of aerodynamic shape, load bearing and deducing the radar cross section(RCS). Usually, LD structure is composed of radar-transparent skins, radar absorbing materials and load-carrying structures. The LD structure of an UAV’s winglet wasstudied in the thesis.An integrated design process for LD structure was obtained and an effective design tool was developed for engineers. The thesis focuses on the follows:1)The state-of-the-art LD structure schemes applied in the wings was reviewed. Based on the UAV winglet’s structure features and demandsof structure/electromagneticperformance, a new LD structure scheme was presented.2) In order to analysis the LD structure’s mechanical behavior, the finite element method(FEM)was chosen as the analysis method according to the comparison of somecommonly used methods. The parameterized model and the FEM modeling method were described in detail. The modeling and analysis processes were automated using PATRAN secondary development language PCL. The results of FEM analysis were studied, which provided the bases for structural optimization.3)Based on analyses among several RCS prediction methods and structural features of winglet LD structure, it is concluded that thefinite-difference time-domain(FDTD) method is the most suitable method for the numerical simulations of LD wing structures. The parametric method of electromagnetic modelingwas presented and the modeling process was automated using the secondary development tool NX Open for Grip of UG. The electromagnetic analysis process was automated by utilizing script mechniques of the electromagnetic simulation software- CST. The accuracy of FDTD method was verified by comparison to the standard case. For winglet LD structure, the influence of mesh quantity to calculation reliability was studied,and the reasonable interval of mesh quantity was determined.4)A wing LD structure integrated design process was created based on automatic structural and electromagnetic analysis techniques and engineering considerations. The structural optimization is realized by invoking iSIGHT8.0’s multi-objective genetic algorithm-NCGA throughthe developing language MDOL in iSIGHT8.0, and the reduction of RCS is achieved by human-mechine interaction procedure. The integrated design process was proved to be feasible by applying it to winglet LD structure design.5) According to the LD structure integrated design process, a wing LD structure integrated design platform was developed using VB.NET. The platform consists of all the functions in process above. Moreover, two optimization methods were added to help reducing RCS of the structure. One optimization methodis from software iSIGHT and another one is an open source optimization code BOBYQA. The two methods give the potential of further improving the performance of LD structure. The platform provides an easy-to-use and efficient design tool for engineers.