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Fatigue Life Prediction of Composite Laminate Based on Stress of Fiber and Matrix of UD Composite
주영식,김민성 한국항공우주학회 2022 International Journal of Aeronautical and Space Sc Vol.23 No.2
This study investigates fatigue life prediction methodologies to establish a fatigue life evaluation technology for composite structures. Owing to the anisotropy of composite materials, a significant difference can be observed in their fatigue lives depending on stacking sequences or load directions. The fatigue life of a composite is closely related to the fatigue properties of its fiber and matrix. Depending on the mechanical contribution of the composite, its mechanical properties as well as fatigue life characteristics vary. In this study, the S–N data of fibers and matrixes were generated based on the fatigue test results and used as the basic fatigue properties for fatigue life prediction. The principal stress of the fiber and matrix was used to predict the fatigue life of laminates with different stacking sequences. To correct the mean stress of the fatigue loads, the Goodman equation was normalized using tensile and compressive strength. A comparison of the life prediction and test results of composite laminates demonstrated that the proposed methodologies predicted the test results well.
주영식,김재훈 한국군사과학기술학회 2002 한국군사과학기술학회지 Vol.5 No.4
This paper introduces the calibration results of the fatigue crack growth models for damage tolerance analysis of the aircraft structures. Generalized Willenborg model and Wheeler model are calibrated with experimental data tested under the load spectrum of a trainer. The retardation factors such as, shut-off ratio in Generalized Willenborg model and shaping exponent in Wheeler model, are evaluated for aluminum alloys AL2024-T3511, AL7050-T7451 and AL7075-T73511. It is shown that the retardation effect of the crack growth rate depends on the yield strength of material and the maximum stress in the load spectrum. Generalized Willenborg model and Wheeler model give satisfactory prediction of crack growth life but the calibration of the experimental parameters with test is required.
주영식,전우철,변관화,조창민,Joo, Young-Sik,Jun, Woo-Chul,Byun, Kwan-Hwa,Cho, Chang-Min 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.4
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.
주영식,전우철,변관화,조창민 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.4
접이식 복합재 날개를 개발하여 중거리 GPS 유도 키트에 적용하였다. 날개는 항공기 장착을 위한 피벗과 양항비 증대를 위해 고세장비를 가지고 있다. 구조설계 요구조건을 만족하기 위하여 날개는 가벼워야할 뿐만 아니라 충분한 강도와 강성을 가지고 있어야 한다. 날개는 탄소섬유/에폭시 복합재로 설계되었으며, 제작비용을 줄이기 위해 일체형 구조로 설계/제작되었다. 구조성능을 검증하기 위해 하중해석 및 비행하중개관시험, 정적구조해석 및 시험, 지상진동시험 및 플러터해석을 수행하였으며, 이를 통하여 날개는 구조설계 요구조건을 만족하는 충분한 구조 강도와 강성을 가지고 있음을 확인하였다. The pivoting composite wing is developed for the mid-range GPS guided kit. 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.
Vibration Fatigue Analysis for Structural Durability Evaluation Under Vibratory Loads
주영식,이종천 한국항공우주학회 2021 International Journal of Aeronautical and Space Sc Vol.22 No.3
The structural integrity of aircraft structures under vibratory loads is primarily evaluated through vibration tests, but it is necessary to predict the design life through vibration fatigue analysis at the design stage. Vibratory loads affect the durability of aircrafts by combining with the dynamic characteristics of their structures. The generation of stress spectrum in the vibratory loads, which must be calculated from power spectral density, is different from the calculations in the time domain. In this study, the stress spectrum generation and fatigue life were analyzed for various frequency bands with different characteristics. Through comparison of the fatigue life in the frequency domain and time domain, the characteristics of the stress spectrum estimation and optimal calculation methods are presented. It was confirmed that the frequency domain results tend to be more conservative in most cases than the time domain results, and Dirlik’s procedure estimates accurately in all frequency bands. A simple correction of the Narrow-band and Steinberg results could increase the accuracy of the fatigue life prediction.