Landing Gear Brake Case Study

Structural and Thermal Optimization of Landing Gear Brake Disc of Boeing 737

1Yash Vashi

Student, Vellore Institute of Technology, Vellore

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Abstract: The aircraft landing gear undergoes severe stress and temperature gradient within a short span of time from braking to full stop. The kinetic and the potential energy of the aircraft is converted to the rotational energy by the wheels, which is then transformed to heat energy through braking systems. The current generation of braking systems consist of an array of stators and rotors lined up together in a T-formation incorporated within the hub of the wheel. The rotors are connected to the wheel hub via the torque tube and rotate with the

In case of a RTO, the aircraft has already achieved V1 speed (Take-off Decision Action Speed) and needs to be decelerated from V1 to stop within a limited time and runway length. Otherwise, the aircraft overshoots the runway and a permanent damage would occur. Thus, the brakes need to be designed which can sustain the temperatures and stresses formed during the RTO.

II. MATERIAL SELECTION

Until about 1963, aircraft brakes were made from steel and other iron alloys. The steel brakes were economical and easy to manufacture but heavy. Thereafter, the designers switched to Beryllium, which was selected for the Lockheed C-5A. Beryllium, although lighter was highly toxic due to formation of Beryllium oxide which required special precautions when handling the material.

Subsequently, carbon brakes were introduced. The carbon-carbon brakes consist of carbon fibres embedded in a carbonaceous matrix. However, they were not ubiquitous as the cost of manufacture was high and thus were restricted to high-performance aircrafts such as military and long-haul commercial jets aircrafts like Lockheed C5-B and Concorde. The cost is recovered due to low weight and longer service life provided by the carbon brakes (Currey,

1. Carbon-Carbon (C/C) Composite: It is used in aircrafts, spacecrafts and F1 race cars primarily as a brake material, engine component and heatshield. The material is light, strong and can be used at temperatures over 3000 ℃ without any loss in performance. (Manocha Lalit M., 2003).

As it is used in extreme environments with elevated temperature and pressure, it is prone to oxidation. To inhibit oxidation process, matrix modification with silicon, zirconium or by multilayer oxidation protection coatings consisting of silicon carbide is done.

C/C composites comprise of non-homogeneous structures like fibres, matrix and pores, and all of them combine to give a diversity of microstructures and owing to its complexity; it is difficult to predict the thermal carrying capacity (Manocha Lalit M., 2003). Other drawbacks are inhomogeneity, insufficient stability of friction coefficient cause due to humidity and high-cost of