Life Prediction Based on Material State Changes in Ceramic Matrix Composite Materials

The concept of prognosis is typically discussed in terms of mechanical characteristics such as structural integrity, durability, damage tolerance, fracture toughness, etc. These familiar concepts are usually addressed by considering balance equations, crack growth relationships, and constitutive equations with constant material properties, and constant or cyclically applied load conditions. Loading histories are represented by changing stress (or strain) states, only. But for many situations, especially associated with high performance engineering structures, the local state of the material may also change during service, so that the properties used in those equations are functions of time and history of applied conditions. But for many energy systems, a broader definition is required. For example, in fuel cells, properties such as conductivity and electrochemical character are altered by material degradation, so that "property fields" replace the global constants in multiphysics balance equations, and time and history enter into the governing equations. The present paper will examine a small set of such problems which involve novel experimental methods of following the accumulation of distributed damage and changes in material state. Specifically, the paper discusses this problem in the context of material state changes measured by impedance variations as a method of following and interpreting those changes in terms of functional performance. The application of these concepts is extended from mechanical structures to energy systems, wherein the material state changes result in variations in electrochemical properties that directly control functional performance of devices such as fuel cells.

Three different oxide/oxide ceramic matrix composite (CMC) materials are described. Design concepts for the attachment of the CMC component to the metal structure of the gas turbine are developed in a first work stream focused on the combustion chamber and the turbine seal segment. Issues like environmental barrier coating (EBC)/thermal barrier coatings (TBC), application and volatilization, allowance for the different thermal expansion and the mechanical fixation are addressed. The design work is accompanied by CFD and FEM simulations. A variation of the microstructural design of the three oxide/oxide CMC materials in terms of different fiber architecture and processing of matrix are considered. Also, mechanical properties of these variations are evaluated. The material concepts are developed further in a second work stream. The CMCs are tested in various loading modes (tension, compression, shear, off-axis loading) from room temperature to maximum application temperature focusing on tensile creep behavior. By modification of the matrix and the fiber-matrix interface as well as EBC coatings, the high temperature stability and the insulation performance are enhanced. An outline of the “High Performance Oxide Ceramic”-program HiPOC for the following years is given, including manufacturing of a high-pressure tubular combustor and turbine seal segments from the improved materials as technology samples, for which validation testing up to technology readiness level 4 is scheduled for 2011.

On this Phase I SBIR project, Creare’s overall objective was to develop and transition a technology that will increase cutting tool life and reduce overall production costs of machining ceramic matrix composite (CMC) materials. We successfully demonstrated the feasibility of machining CMC materials using the Laser-Assisted Machining (LAM) approach, which utilizes a laser to preheat a thin layer of the CMC material prior to its removal using conventional machine tools. In particular, we demonstrated that the cutting forces were reduced by as much as 40% compared to conventional machining processes. This reduction enables increased processing speeds which decrease cycle times and overall processing costs. Additionally, we developed and validated a comprehensive thermal model for the edge machining of CMCs. When combined with the experimental results, the temperatures near the material removal interface for the optimal LAM condition were predicted.

In this study, a new composite ceramic material using a red clay matrix with different amount of clinker from the cement industry has been developed. The aim is to valorize some natural resources such as red clay and sub-products from the cement industry as clinker in order to develop new materials for industrial and/or catalytic uses. Raw materials were grounded in order to reduce the particle size and obtain a homogeneous slip. The samples were mixed and compressed into pellets and undergo a heat treatment up to 1100℃. Geotechnical characterization has been carried out. Firing proprieties (shrinkage, water absorption, and mechanical resistance to the inflection) were measured. The composition of the ceramic material was investigated by X-ray diffraction, XRF, SEM and EDS methods. The incorporation of clinker in the ceramic composite material up to 50 wt% exhibits good behaviors (physical and mechanical proprieties) and can be used as a ceramic product.

Further development of ceramic materials for total hip replacement aim to increase fracture toughness and further reduce the incidence of bearing fracture. Edge loading due to translational mal positioning (microseparation) has replicated stripe wear, wear rates, and bimodal wear debris observed on retrievals. This method has replicated the fracture of early zirconia ceramic-on-ceramic bearings. This has shown the necessity of introducing microseparation conditions to the gait cycle when assessing the tribological performance of new hip replacement bearings. Two novel ceramic matrix composite materials, zirconia-toughened alumina (ZTA) and alumina-toughened zirconia (ATZ), were developed by Mathys Orthopädie GmbH. In this study, ATZ-on-ATZ and ZTA-on-ZTA bearing combinations were tested and compared with alumina-on-alumina (Al2O3-on-Al2O3) bearings under adverse microseparation and edge loading conditions using the Leeds II physiological anatomical hip joint simulator. The wear rate (±95% confidence limit) of ZTA-on-ZTA was 0.14 ± 0.10 mm(3)/million cycles and that of ATZ-on-ATZ was 0.06 ± 0.004 mm(3)/million cycles compared with a wear rate of 0.74 ± 1.73 mm(3)/million cycles for Al2O3-on-Al2O3 bearings. Stripe wear was evident on all bearing combinations; however, the stripe formed on the ATZ and ZTA femoral heads was thinner and shallower that that formed on the Al2O3 heads. Posttest phase composition measurements for both ATZ and ZTA materials showed no significant change in the monoclinic zirconia content. ATZ-on-ATZ and ZTA-on-ZTA showed superior wear resistance properties when compared with Al2O3-on-Al2O3 under adverse edge loading conditions.

To date, several polymer-derived ceramic fibers have been developed all over the world, out of which SiC fibers synthesized from polycarbosilane and their derivatives have achieved highest heat resistance and show excellent mechanical properties. Their use in ceramic matrix composite materials has resulted in high-temperature stability and light weight, which show great promise in next-generation applications, such as aerospace engines. This book presents polymer-derived ceramic fibers from a historical viewpoint; basic information about them, such as production process, fine structures, and physical properties; their applications; and prospects of future inorganic fibers.

C/C–SiC composites for space applications and advanced friction systems

Composite ceramic materials reinforced with carbon fibers are interesting materials because of their excellent mechanical and thermo-physical properties, which make them appropriate for many applications, including re-entry shields, rocket nozzles, disc brakes, and prosthetic devices. For all these purposes, many different types of such materials have been developed, for example, carbon/silicon-carbide or carbon/carbon–silicon-carbide composites that are commonly produced from carbon/carbon composites impregnated with liquid silicon by the liquid-silicon infiltration (LSI) process. In this work, a new ceramic matrix composite friction material for brake discs was developed that combines a high fracture toughness with good oxidation and abrasion resistance, good thermal conductivity, and the appropriate friction characteristics. For the production of such materials, the “dual-matrix” approach combined with reactive sintering was used. The materials have suitable mechanical properties and the braking discs have appropriate coefficient of friction and very low wear rate.

Determination of the correlation of characteristics of consolidated body with content, size, distribution in matrix and shape factor of porous phase. The goal of the following paper is to determine formula for correlation between characteristics of ceramics and ceramic composite materials and porous phase, which is the weakest part of material. This will allow theorists and practicists to correctly choose and improve technologies and technical processes. According to the study and analysis of micro- and macrostructural, micro-and macromechanical of ceramics and ceramic composite materials, parameters of the formula was determined. Formula contains macromechanical properties. When detail is completely decomposed: mechanics on bending by three or four-point load, mechanics on shrinking, breaking, impact resistance. Morphologic characteristics: Porous phase content in the matrix and its distribution, size, shape factor of pores. Correlation of given factors with others structural characteristics, such as: crystal and glass phases. Novel determination of pore distribution factor is given. Created formula has collective nature and using it allows researchers and practicists to correctly plan and precisely preform all the positions of the technological production.

Effects of sintering parameters on microstructure, graphene structure stability and mechanical properties of graphene reinforced Al2O3-based composite ceramic tool material

New composite ceramic materials enable to improve mechanical properties and various performances more than monolithic ceramic materials. Generally, composite ceramic materials include more than two different materials, in addition, more than two crystal structures in case of α and β crystal phase composite Si3N4 material in this research. Composite ceramic materials enable to get various different characteristics that show excellent properties, not only mechanical properties but electrical properties, resistance to oxidation and wear. Properties improvement develops many new applications with superior performance more than conventional materials. In this research, we have developed various ceramic reinforced composite, based on Al2O3 and ZrO2 ceramics with carbide and nitride particles or whisker addition. Farther more we have developed α and β crystal phase composite Si3N4 material by researching the sintering additives stoichiometric ratio and sintering condition. Finally we succeeded in applying ceramic composite materials to various industrial parts, for example, Al2O3-TiC thin magnetic slider substrate, Al2O3-SiC whisker based cutting tool, Si3N4 squeezing roll and wear parts, ZrO2-WC ceramics punch and die for high speed pressing.

Errors assessment for spectral emissivity measurements collected from a SiNC ceramic matrix composite material using a 1.6 μm single wavelength pyrometer

Due to the remarkable physical and mechanical properties of individual, perfect carbon nanotubes (CNTs), they are considered to be one of the most promising new reinforcements for structural composites. Their impressive electrical and thermal properties also suggest opportunities for multifunctional applications. In the context of inorganic matrix composites, researchers have particularly focussed on CNTs as toughening elements to overcome the intrinsic brittleness of the ceramic or glass material. Although there are now a number of studies published in the literature, these inorganic systems have received much less attention than CNT/polymer matrix composites. This paper reviews the current status of the research and development of CNT-loaded ceramic matrix composite (CMC) materials. It includes a summary of the key issues related to the optimisation of CNT-based composites, with particular reference to brittle matrices and provides an overview of the processing techniques developed to optimise dispersion quality, interfaces, and density. The properties of the various composite systems are discussed, with an emphasis on toughness; a comprehensive comparative summary is provided, together with a discussion of the possible toughening mechanism that may operate. Last, a range of potential applications are discussed, concluding with a discussion of the scope for future developments in the field.

Alumina‐Zirconium dioxide (Al2O3‐ZrO2) Ceramic Composite Material (CCM) is specifically known for its enhanced mechanical and corrosion resistance properties and is widely used as raw material for mechanical parts like, pump components, die inserts, bearings, etc. As a result, industrialists are searching for an efficient method for machining this Al2O3‐ZrO2 material. In this regard, a hybrid unconventional machining process called Electrochemical Discharge Machining (ECDM) is adapted to analyze the machinability of Al2O3‐ZrO2 CCM. Besides, to ensure the efficiency of the ECDM process, a magnetic field is also given to the tool electrode during this study to improve the Material Removal Rate (MRR) of the ECDM machine. The experiment is designed using Response Surface Methodology (RSM) by changing the magnitudes of input controls, namely Electrolytic Concentration (EC), Inter‐electrode Gap (IEG) and Applied Voltage (AV). Moreover, a novel hybrid machine learning optimization strategy called Deep Belief Network based Battle Royal Optimization (DBN‐BRO) algorithm is developed to predict and optimize the ECDM process. Finally, the optimum results are perceived from 55 V AV, 22.727% EC and 40.909 mm IEG input levels. The proposed method shows less than 0.6207 Root Mean Square Error (RMSE) and tools nearly 80 iterations for optimizing the results.

The Sydney octopus (Octopus tetricus) occurs in unusual numbers on a shell bed of its prey remains that have accumulated as an extended midden where additional octopuses excavate dens. Here, O tetricus are ecosystem engineers, organisms that modulate availability of resources to other species and to their own species by causing physical state changes in materials. A community of invertebrate grazers and scavengers has developed on the shell bed. Fishes are attracted to the shell bed in numbers significantly greater than in nearby habitats. Large predators, including wobbegong sharks, were attracted to and fed on concentrations of fish, inhibiting the activities of the original engineers, the octopuses. Positive feedbacks included the accumulation of shell debris, increasing shelter availability for additional octopuses and aggregating fish. Negative feedbacks included reductions of nearby prey size and availability, aggression among octopuses, and predator limitation to octopus activity that would otherwise maintain the shell bed.