Longbiao Li

By Li Longbiao

In this chapter, the hysteresis behavior of fiber-reinforced ceramic-matrix composites (CMCs) is investigated. Based on the interface slip state inside of CMCs, the hysteresis loops can be divided into four different cases. The relationship between the internal damage and the hysteresis loops of CMCs is established. Using the experimental hysteresis loops, the fiber/matrix interface frictional coefficient can be obtained. The mechanical hysteresis loops and the fiber/matrix interface frictional coefficient of SiC/CAS and C/SiC composites are predicted using the present models. When the fiber/matrix interface frictional coefficient decreases under cyclic fatigue loading, the fatigue hysteresis loops, fatigue hysteresis dissipated energy, fiber/matrix interface debonding, and slip all change. The fatigue hysteresis dissipated energy first increases and then decreases with decreasing interface frictional coefficient.

Part of the book: Hysteresis of Composites

By Li Longbiao

In this chapter, the matrix cracking of fiber-reinforced ceramic-matrix composites (CMCs) is investigated using the energy balance approach. The relationship between the matrix cracking stress, fiber and interface oxidation, and fiber failure is established. The effects of the fiber volume, interface shear stress and interface debonding energy, fiber failure, and oxidation temperature on the time-dependent matrix cracking stress are analyzed. The experimental matrix cracking stress of different fiber-reinforced CMCs is predicted using the present models.

Part of the book: Hysteresis of Composites

By Sherkhan Aitugan and Longbiao Li

This chapter outlines the results of risk analysis and economic analysis of commercial aero engines during aircraft operation. Risk analysis is the procedure for identifying risk factors and assessing their significance, in essence, analysis of the likelihood that certain undesirable events may occur and as such adversely affect operation. Risk analysis includes risk assessment and methods to reduce risks or reduce adverse effects associated with it. Furthermore, economical analysis is a scientific way of understanding the essence of economic phenomena and processes, which in turn are based on dividing them into their constituent parts. In doing so, the variety of relationships and dependencies aimed at improving the associated work through the development and implementation of optimal solutions is studied. The purpose of the economic analysis is to give management of the actual state, and for persons who are not directly working with it, but are interested in its financial condition, the information necessary for an impartial judgment.

Part of the book: Safety and Risk Assessment of Civil Aircraft during Operation

By Longbiao Li

In this chapter, the risk assessment methods for aircraft system, structure, and aeroengine are investigated. For the aircraft system risk assessment, the probability level is divided into probable, improbable, and extremely improbable, and the hazard level of the failure condition is divided into minor, major, and catastrophic. Using Weibull analysis and Bayesian method to analyze the aircraft operation data, the risk level of aircraft system can be determined by combing methods provided in AC 25.1309-1A. For the aircraft structure risk assessment, the probability fracture mechanics approach can be used to determine the structure failure risk based on the data of material properties, environment, inspection, and so on. For the aeroengine risk assessment, the methods for classification of failure risk level, determination of hazard ratio, and calculation of the risk factor and risk per flight are given. The risk assessment process for aeroengine multi-failure modes based on the Monte Carlo simulation is presented to predict the occurrence of the failure and assess the failure risk.

Part of the book: Safety and Risk Assessment of Civil Aircraft during Operation

By Longbiao Li

Part of the book: Air Traffic Management and Control

By Longbiao Li

Part of the book: Next Generation Fiber-Reinforced Composites

By Longbiao Li and Dmytro Tiniakov

The development of the aviation industry depends on many factors. One of the most important factors is the development of power units. A power plant is a source of energy for an airplane. Without power units, flight is possible, but the transportation efficiency of such flights will be low. So, an in-depth analysis of the power unit structure is an actual task every time. The power unit is composed of several components. Obviously, the main structural element is the engine. However, the overall efficiency of the propulsion unit does not depend only on the engine. Subsystems and subcomponents of power units should have rational performance that can provide high overall efficiency. So, a detailed analysis of each of these structural members is also an actual task. To perform such an analysis, it is necessary to know the characteristics of these components and ways to increase their efficiency. In this chapter, all these features are briefly explained. In addition, some trends for the future development of civil aircraft power units are discussed.

Part of the book: Propulsion Systems

By Longbiao Li

Ceramic-matrix composites (CMCs) are a class of materials that combine the high-temperature stability and strength of ceramics with the toughness and damage tolerance of fibers. One of the key advantages of CMCs is their ability to withstand high temperatures, making them ideal for applications in gas turbines, rocket nozzles, and heat exchangers. The high-temperature stability of CMCs is due to the ceramic-matrix material, which has a high melting point and excellent thermal conductivity. This allows CMCs to operate at temperatures above 1000°C, where traditional metal alloys would fail. These composites have gained significant attention in recent years due to their potential for use in a wide range of applications, including aerospace, automotive, energy, and defense. This chapter reviews the recent progress in the design, application, and challenges in CMCs, especially the hot-section components design and testing at elevated temperatures.

Part of the book: Fiber-Reinforced Composites