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Haziran 3, 2022

Kompozit skid iniş takımı tasarım araştırması hakkındaki bilgiler aşağıda yer almaktadır.

Rotary winged aircraft traditionally use one of two types of landing gear systems. The oleo-strut landing gear with wheels offers advantages of initial taxi and take-off run capability but at the cost of design complexity. Skid landing gears on the other hand offer simplicity in design and reduction in empty weight (WE). Currently skid landing gears are manufactured from metal alloys such as Aluminum 7075. The elasto-plastic properties of such metals offer significant energy dissipation capabilities during plastic bending. FAR Part 271 regulations permit yielding of the landing gear under limit load conditions. When subjected to crash loads, metal plastically deforms, absorbing energy and allowing the fuselage underbelly to crash in a controlled crashworthy manner.

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Haziran 3, 2022

Dört noktalı eğilme altında kompozit laminatların kırılma davranışı hakkındaki bilgiler aşağıda yer almaktadır.

In this study, failure behavior of fiber-reinforced composites under four-point bending is investigated.
First, the tests are modeled analytically using the classical lamination theory (CLT).
The maximum allowable moment resultants of off-axis laminate as well as balanced and symmetric angle-ply  composite laminates as a function of fiber orientation angle, are obtained using Tsai-Wu, maximum stress, maximum strain, Hashin, Tsai-Hill, Hoffman, quadric surfaces, modified quadric surfaces, and Norris failure criteria. Second, the same tests are simulated using the finite element method (FEM). Thermal residual stresses are calculated and accounted for in the failure analysis.
An analysis is conducted for optimal positioning of the supports so as to ensure that intralaminar failure modes dominate interlaminar (delamination) failure mode.
A test setup is then constructed accordingly and experiments are conducted. The correlation of the predicted failure loads and the experimental results is discussed. The quadric surfaces criterion is found to correlate better with the experimental results among the chosen failure criteria for the selected configurations.
Fazil O Sonmez, Department of Mechanical Engineering, Bogazici University, Istanbul

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