Young-Sik Joo

Optimization of Radar Absorbing Structures for Aircraft Wing Leading Edge

In this paper, objective functions are defined for optimization of radar absorbing structures (RAS) on the aircraft wing leading edge. RAS is regarded as a single layer structure made of dielectrics. Design variables are the real and imaginary parts of complex permittivity. Reflection coefficient(RC) and radar cross section(RCS) are used in the objective function respectively. Transmission line theory is employed to calculate the RC. The RCS is evaluated by using physical optics(PO) for a leading edge part model. Genetic algorithm(GA) is used to perform optimization procedures. The radar absorbing performance of designed RAS is assessed by the RCS of a wing which has RAS on the leading edge.

Full Scale Durability Test of Basic Trainer

The general requirements to achieve the structural integrity of the airframe are described in the military specification, MIL-STD-1530A. One of these requirements is the durability and damage tolerance of the airframe, which should be shown through the analysis and test based on the related specifications. This paper introduces the full scale durability test to evaluate the structural safety and durability of the basic trainer, KT-1. The test was performed according to the procedure in the military specification. The flight by flight load spectrum was developed by KT-1 fatigue load criteria and used for the durability test. The durability test had been performed for 4 service lives and was completed successfully. Therefore, it was shown that KT-1 airframe satisfied the durability requirements.

Development of a composite EM wave absorber for the leading edge of low observable aircraft

In this study, an Electromagnetic (EM) wave-absorbing composite structure design is proposed. The conventional composite EM wave absorber contains lossy fillers for dielectric characteristics, and thus the fillers affect the mechanical properties, which determine the structural performance of the composite itself. The newly proposed EM wave absorber uses a combination of the following two components: the load-bearable composite structure as the ‘shell’ and the EM wave-absorbing back layer as the ‘absorber.’ The shell type absorber does not use any additional fillers in the composite structure. However, the absorbing layer that is designed with a periodic patterned layer and low lossy foam exhibits good EM wave-absorbing performance. Design, analysis with computational simulation, and measurement of EM characteristics are performed to verify the advantages of the shell type absorber. Furthermore, the EM wave absorber is adopted in the leading edge of an aircraft to identify the contribution of Radar Cross Section reduction. This type of absorber has various applications in aerial vehicles, and the EM characteristics are widely tunable for specific purposes without changing the original shell structure.

A Development of Pivoting Composite Wing for Mounting Kit

ABSTRACT The pivoting composite wing is developed for the kit to be mounted on the external stores. The wing has a pivoting structure for the installation to an aircraft and high aspect ratio to increase lift drag ratio. The wing needs to be light and have sufficient strength and stiffness to satisfy structural design requirements. The wing is designed with carbon fiber composite and the structural parts are integrated to reduce cost to manufacture. In order to verify the structural performances, the design load analysis and flight load survey, the static analysis and test, the ground vibration test and flutter analysis are performed. It is shown that the wing has sufficient structural strength and stiffness to satisfy the structural design requirements.Keywords : Composite Wing(복합재 날개), High Aspect Ratio(고세장비), Flight Load Survey(비행하중개관), Static Analysis and Test(정적해석 및 시험), Ground Vibration Test(지상진동시험), Flutter Analysis(플러터해석) 1. 서 론 외부장착물의 키트로 사용하기 위한 접이식의 복합재 날개를 개발하였다. 날개는 동체에 피벗으로 체결되어 날개가 접힌 상태로 항공기에 탑재되며, 자율 비행 동안에는 펼쳐질 수 있도록 설계되어 있다 . 날개는 장거리 비행에 필요한 양항비(Lift Drag Ratio)의 향상을 위하여 고세장비(High Aspect Ratio)의 익형 구조를 가지고 있으며, 날개에는 조종면인 플래퍼론과 유선형 덮개가 장착되어 있다. 외부장착물이 원거리까지 비행할 수 있도록 경량화하고 제작비용을 줄이기 위한 구

A Study on Manufacture of Integrated Composite Wing with High Aspect Ratio

In this paper, the study for the manufacture of the integrated composite wing is performed. The wing has a pivoting structure and high aspect ratio to increase lift drag ratio. The wing is designed with carbon fiber composite because the wing needs to be light and have sufficient strength and stiffness to satisfy structural design requirements. The number of structural members is decreased by part integration to reduce manufacturing cost and the wing is manufactured with the integrated molding process by an autoclave. The material properties are identified by the coupon tests and the structural strength and stiffness are verified through the component tests.

Case Study of F-15 Airframe Battle Damage Repair Design and Assessment Procedure

For the purpose of facing battle damage that a fighter is subject to in combat, following recovery procedures such as damage assessment, repair design and structural integrity evaluation are investigated. A sample study is presented on the battle damage of F-15 ECS bay, which is comprised of damage assessment and repair design based on ABDR(Aircraft Battle Damage Repair) skills and work procedure complying with AFTO(Air Force Technical Order) forms. Further, the flight safety of repaired structure is validated and the time the permanent repair should be done is estimated through the evaluation of structural integrity such as the calculation of static strength and fatigue life.