Multiple Matrix Cracking of Fiber-Reinforced Ceramic-Matrix Composites during Operation

In the field of civil aviation, the most important factor is safety quality. Improving aircraft performance can increase flight safety factor in some degree. To improve the thrust-to-weight ratio of aircraft engines and reduce fuel consumption, the fundamental measure is to increase the turbine inlet temperature of engines, while hot-section components is directly related to the maximum allowable operating temperature. Ceramic-matrix composite (CMC) material is one of the important candidate materials for aeroengine. To improve CMCs in aircraft engine application, it is necessary to investigate the failure mechanism of CMCs and also failure models. However, during operation, matrix multiple cracking occurs with fiber debonding and fracture, which affects the flight safety and failure risk. In this chapter, the multiple matrix cracking of fiber-reinforced CMCs is investigated using energy balance approach.

The Effect of Random Load on Life Prediction of High-Temperature Ceramic Matrix Composites

High-temperature ceramic matrix composites (CMCs) are widely used in hot section components of aeroengine, and random loads have an important effect on their safety and reliability during aircraft operation. The current fatigue life prediction model of CMC is divided into macrophenomenon model and microdamage mechanism model. In this chapter, the fatigue life of fiber-reinforced ceramic matrix composites is investigated. The fatigue life of the fiber-reinforced ceramic matrix composites is predicted by micromechanical methods. The effect of random loading on fatigue life is analyzed and compared with constant peak stress fatigue life. The influence of composite constitutive properties on fatigue fracture is also discussed.

Risk Assessment of Civil Aircraft during Operation

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.

Air Traffic Controllers’ Attitude to the Mistakes Hazards during Their Professional Experience

Air traffic controllers’ (ATCs) work process can be presented as uninterrupted set of decisions. These decisions occur and are implemented in both clear and stealth forms being influenced a lot. Determined and stochastic risks are especially important in this process. Human factor (HF) effect on flight safety is proven to be better considered through operators’ attitudes toward unsafe acts and conditions. This seamlessly integrates in ICAO safety paradigm. Air traffic controllers’ preferences system (PS) is discussed in regard to typical professional mistakes set. Using paired comparison, normative part of summary hazard and differentiating part of summary hazard, the preferences system of air traffic controllers is received. For the first time, mistakes pair summary hazard is determined on the unique qualimetric 100-point scale. Systems pair has high correlation level according to Spearman coefficient (R = 0.9727). Proposed Kendall rank coefficient outweighs the traditional one twice (Wtraditional = 0.2722, Wproposed = 0.55237). The significance level for all cases is equal to 1%. Multistep procedure of marginal opinions separation is implemented. It increased Kendall rank coefficient value up to Wproposed = 0.7. Survey procedure influenced positively on the ability of mistakes memorization, recognition, and avoidance during simulation training.

Design Approaches for Safety Increasing and Risk Decreasing for the Civil Aircraft’s Operation

The safety and risks of civil aircraft operation depend on a lot of factors. One of them is the structural features of an aircraft. In aviation history, there are examples when “non-rational” design solution was the reason for crashes, but there are examples about successful civil aircraft that have “rational” structure and long operational time without critical incidents. So, how can a designer provide high safety of level and decrease incidents’ risks in time of a regular aircraft operation? This chapter partly can help to understand some reasons and approaches for providing “rational” aircraft structure. Design solutions can be divided into some groups by some common features and requirements. They are maintainability, serviceability, accessibility, labor effort decreasing, weather requirements, transportation, etc. All these groups depend on engineers’ structural solutions. They are interdependent and often contradictory. In other words, if one of the features will be better, another will be worse at the same time. And, a designer must remember all the time about this and try to find compromise between different requirements. The successful commercial aircraft is composed of a set of rational design solutions for these specific tasks.

Safety and Risk Assessment of Civil Aircraft during Operation

Risk and safety are always considered to be the most critical operational characteristics of civil aircraft. Typically, they relate to the possible occurrence of air traffic collisions that could result in loss of life, damage to infrastructure, and damage to property by third parties. Consequently, in addition to other adverse effects such as noise, air pollution, they were deemed externalities. Risk and protection became topics of continuous study, ranging from purely technical/technological aspects to explicitly administrative ones, due to their inherent very high importance. Such concerns require the establishment of appropriate regulations regarding designs and operations of device technology. In order assess the risk, there are several methods which include: identification of safety concerns, analysis of the risk factors likelihood, analysis of the risk factors severity, and assessment and the admissibility of risk factors. And finally, reducing of the risk should be performed by three general strategies which are: avoidance of the risk, reduction of risk, and isolation of the exposure. These strategies are implemented based on efficiency, technical measures, controlled measures, staffing measures, cost/benefit, practicality, acceptability of each party, durability, residual risk factor for flights safety, and new challenges. With the advancement of technology, new methods of risk deduction and safety concerns are being developed to ensure safe and risk-free flight operation.

Theories and Models of Human Errors Occurrence. Simulation of Aircraft Maintenance Processes

General issues of the errors occurrence by technical personnel were considered, their causes and consequences. Classifications of errors based on an ergonomic understanding of their nature, as well as on the results of an engineering-psychological analysis of operators’ activity are given. Much attention is paid to the methods used by ICAO to classify errors and violations. Details considered models SHELL and J. Reason. Their adaptation is presented for analysis cases of the impact of the technical maintenance quality on the flight safety of aircraft. A special place is occupied by the disclosure of assessing issues impact of technical personnel errors on flight safety. A wide range of existing methods and models is presented, allowing obtaining qualitative and quantitative assessment of this effect in order for the prevention of errors by technical personnel and mitigating their consequences.

Finite Element Analysis of Fiber Pull-Out of Ceramic Matrix Composites

Ceramic matrix composites (CMCs) are widely used in aerospace, defense industry, and other fields because of their high strength, high toughness, and high temperature resistance. The interface phase with matching performance and structural coordination is the key element to improve the brittleness of CMCs and improve their strength and toughness. In this chapter, based on the fiber pull-out experiment, using the cohesive zone model as the interface element model, a two-dimensional axisymmetric fiber pull-out finite element model was established and simulated. The results show that within a certain range, higher interface bonding strength and interface fracture energy increase the maximum debonding load during fiber pull-out and enhance the material bearing capacity.

Modeling of Damage Evolution of Fiber-Reinforced Composite Structure

This chapter is the result of a study of many special disciplines, such as damage of matrix, cracking, interface, debonding, and fiber failure. A damage mechanics model is presented to characterize brittle failure in elastic fiber-reinforced composite materials. During the life of the aircraft, cracks and damage can occur in aviation structures that should be analyzed to determine the decrease in stiffness and resistance due to the presence of the cracks. Theoretical and numerical problems related to intralaminar and interlaminar failure modeling are very well discussed. The formulations of the constitutive models presented in this chapter support the Continuum Damage Mechanics (CDM) approach and enable the control of energy dissipation in relation to each failure mode, regardless of the refinement of the network and the orientation of the fracture plane. In context to CDM, internal thermodynamic irreversible damage variables are defined to quantify the damage concentration in relation to each possible failure mode and to predict the gradual reduction in stiffness for each bond layer. Numerical examples are provided to possibly explain the capabilities of the model.

Non-Steady First Matrix Cracking of Fiber-Reinforced Ceramics

Matrix cracking affects the reliability and safety of fiber-reinforced ceramic-matrix composites during operation. The matrix cracking can be divided into two types, that is, steady state crack and non-steady state cracking. This chapter is about the non-steady stable cracking of fiber-reinforced CMCs. The micro stress field of fiber, matrix, and interface shear stress along the fiber direction is analyzed using the shear-lag model. The relationship between the crack opening displacement and the crack surface closure traction is derived. The experimental first matrix cracking stress of different CMCs are predicted.