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1 – 10 of 15This paper aims to predict fatigue life and fatigue limit of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e. unidirectional, cross-ply, 2D-…
Abstract
Purpose
This paper aims to predict fatigue life and fatigue limit of fiber-reinforced ceramic-matrix composites (CMCs) with different fiber preforms, i.e. unidirectional, cross-ply, 2D-, 2.5D- and 3D-woven, at room and elevated temperatures.
Design/methodology/approach
Under cyclic loading, matrix multicracking and interface debonding occur upon first loading to fatigue peak stress, and the interface wear appears with increasing cycle number, leading to degradation of the interface shear stress and fibers strength. The relationships between fibers fracture, cycle number, fatigue peak stress and interface wear damage mechanism have been established based on the global load sharing (GLS) criterion. The evolution of fibers broken fraction versus cycle number curves of fiber-reinforced CMCs at room and elevated temperatures have been obtained.
Findings
The predicted fatigue life S–N curve can be divided into two regions, i.e. the Region I controlled by the degradation of interface shear stress and fibers strength and the Region II controlled by the degradation of fibers strength.
Practical/implications
The proposed approach can be used to predict the fatigue life and fatigue limit of unidirectional, cross-ply, 2D-, 2.5D- and 3D-woven CMCs under cyclic loading.
Originality/value
The fatigue damage mechanisms and fibers failure model were combined together to predict the fatigue life and fatigue limit of fiber-reinforced CMCs with different fiber preforms.
Details
Keywords
Mica Grujicic, Rohan Galgalikar, S. Ramaswami, Jennifer Snipes, Ramin Yavari and Rajendra K. Bordia
A multi-physics process model is developed to analyze reactive melt infiltration (RMI) fabrication of ceramic-matrix composite (CMC) materials and components. The paper aims to…
Abstract
Purpose
A multi-physics process model is developed to analyze reactive melt infiltration (RMI) fabrication of ceramic-matrix composite (CMC) materials and components. The paper aims to discuss this issue.
Design/methodology/approach
Within this model, the following key physical phenomena governing this process are accounted for: capillary and gravity-driven unsaturated flow of the molten silicon into the SiC/SiC CMC preform; chemical reactions between the silicon melt and carbon (either the one produced by the polymer-binder pyrolysis or the one residing within the dried matrix slurry); thermal-energy transfer and source/sink phenomena accompanying reactive-flow infiltration; volumetric changes accompanying chemical reactions of the molten silicon with the SiC preform and cooling of the as-fabricated CMC component to room temperature; development of residual stresses within, and thermal distortions of, the as-fabricated CMC component; and grain-microstructure development within the SiC matrix during RMI.
Findings
The model is validated, at the material level, by comparing its predictions with the experimental and modeling results available in the open literature. The model is subsequently applied to simulate RMI fabrication of a prototypical gas-turbine engine hot-section component, i.e. a shroud. The latter portion of the work revealed the utility of the present computational approach to model fabrication of complex-geometry CMC components via the RMI process.
Originality/value
To the authors’ knowledge, the present work constitutes the first reported attempt to apply a multi-physics RMI process model to a gas-turbine CMC component.
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Keywords
Mica Grujicic, Jennifer Snipes, Ramin Yavari, S. Ramaswami and Rohan Galgalikar
The purpose of this paper is to prevent their recession caused through chemical reaction with high-temperature water vapor, SiC-fiber/SiC-matrix ceramic-matrix composite (CMC…
Abstract
Purpose
The purpose of this paper is to prevent their recession caused through chemical reaction with high-temperature water vapor, SiC-fiber/SiC-matrix ceramic-matrix composite (CMC) components used in gas-turbine engines are commonly protected with so-called environmental barrier coatings (EBCs). EBCs typically consist of three layers: a top thermal and mechanical protection coat; an intermediate layer which provides environmental protection; and a bond coat which assures good EBC/CMC adhesion. The materials used in different layers and their thicknesses are selected in such a way that the coating performance is optimized for the gas-turbine component in question.
Design/methodology/approach
Gas-turbine engines, while in service, often tend to ingest various foreign objects of different sizes. Such objects, entrained within the gas flow, can be accelerated to velocities as high as 600 m/s and, on impact, cause substantial damage to the EBC and SiC/SiC CMC substrate, compromising the component integrity and service life. The problem of foreign object damage (FOD) is addressed in the present work computationally using a series of transient non-linear dynamics finite-element analyses. Before such analyses could be conducted, a major effort had to be invested toward developing, parameterizing and validating the constitutive models for all attendant materials.
Findings
The computed FOD results are compared with their experimental counterparts in order to validate the numerical methodology employed.
Originality/value
To the authors’ knowledge, the present work is the first reported study dealing with the computational analysis of the FOD sustained by CMCs protected with EBCs.
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Keywords
Donald A. Klosterman, Richard P. Chartoff, Nora R. Osborne, George A. Graves, Allan Lightman, Gyoowan Han, Akos Bezeredi and Stan Rodrigues
A novel rapid prototyping technology incorporating a curved layer building style was developed. The new process, based on laminated object manufacturing (LOM), was designed for…
Abstract
A novel rapid prototyping technology incorporating a curved layer building style was developed. The new process, based on laminated object manufacturing (LOM), was designed for efficient fabrication of curved layer structures made from ceramics and fiber reinforced composites. A new LOM machine was created, referred to as curved layer LOM. This new machine uses ceramic tapes and fiber prepregs as feedstocks and fabricates curved structures on a curved‐layer by curved‐layer basis. The output of the process is a three‐dimensional “green” ceramic that is capable of being processed to a seamless, fully dense ceramic using traditional techniques. A detailed description is made of the necessary software and hardware for this new process. Also reviewed is the development of ceramic preforms and accompanying process technology for net shape ceramic fabrication. Monolithic ceramic (SiC) and ceramic matrix composite (SiC/SiC) articles were fabricated using both the flat layer and curved layer LOM processes. For making curved layer objects, the curved process afforded the advantages of eliminated stair step effect, increased build speed, reduced waste, reduced need for decubing, and maintenance of continuous fibers in the direction of curvature.
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Zhenlong Peng, Aowei Han, Chenlin Wang, Hongru Jin and Xiangyu Zhang
Unconventional machining processes, particularly ultrasonic vibration cutting (UVC), can overcome such technical bottlenecks. However, the precise mechanism through which UVC…
Abstract
Purpose
Unconventional machining processes, particularly ultrasonic vibration cutting (UVC), can overcome such technical bottlenecks. However, the precise mechanism through which UVC affects the in-service functional performance of advanced aerospace materials remains obscure. This limits their industrial application and requires a deeper understanding.
Design/methodology/approach
The surface integrity and in-service functional performance of advanced aerospace materials are important guarantees for safety and stability in the aerospace industry. For advanced aerospace materials, which are difficult-to-machine, conventional machining processes cannot meet the requirements of high in-service functional performance owing to rapid tool wear, low processing efficiency and high cutting forces and temperatures in the cutting area during machining.
Findings
To address this literature gap, this study is focused on the quantitative evaluation of the in-service functional performance (fatigue performance, wear resistance and corrosion resistance) of advanced aerospace materials. First, the characteristics and usage background of advanced aerospace materials are elaborated in detail. Second, the improved effect of UVC on in-service functional performance is summarized. We have also explored the unique advantages of UVC during the processing of advanced aerospace materials. Finally, in response to some of the limitations of UVC, future development directions are proposed, including improvements in ultrasound systems, upgrades in ultrasound processing objects and theoretical breakthroughs in in-service functional performance.
Originality/value
This study provides insights into the optimization of machining processes to improve the in-service functional performance of advanced aviation materials, particularly the use of UVC and its unique process advantages.
Details
Keywords
The purpose of this paper is to provide an insight into the techniques used for the non‐destructive testing (NDT) of non‐metallic structural materials, notably polymer and ceramic…
Abstract
Purpose
The purpose of this paper is to provide an insight into the techniques used for the non‐destructive testing (NDT) of non‐metallic structural materials, notably polymer and ceramic composites.
Design/methodology/approach
Following a short introduction, this paper first considers methods for testing carbon fibre‐ and glass fibre‐reinforced polymer composites. It then discusses the role of NDT in wind and wave power systems and some of the techniques used to test ceramics and ceramic composites. Brief conclusions are drawn.
Findings
This shows that the growing use of non‐metallic engineering materials in critical applications has highlighted the need for a range of advanced NDT methods. While some traditional techniques can be adapted to test these materials, in several instances novel methods are required. These include a range of thermal, ultrasonic, electromagnetic, radiographic and laser‐based technologies.
Originality/value
The paper provides a review of the techniques used and being developed for the non‐destructive testing of non‐metallic engineering materials.
Details
Keywords
Benoit Picard, Mathieu Picard, Jean-Sébastien Plante and David Rancourt
The limited energy density of batteries generates the need for high-performance power sources for emerging eVTOL applications with radical operational improvement potential over…
Abstract
Purpose
The limited energy density of batteries generates the need for high-performance power sources for emerging eVTOL applications with radical operational improvement potential over traditional aircraft. This paper aims to evaluate on-design and off-design recuperated turbogenerator performances based on newly developed compression loaded ceramic turbines, the Inside-out Ceramic Turbine (ICT), in order to select the optimum engine configuration for sub-megawatt systems.
Design/methodology/approach
System-level thermal engine modeling is combined with electric generators and power electronics performance predictions to obtain the Pareto front between efficiency and power density for a variety of engine designs, both for recuperated and simple cycle turbines. Part load efficiency for those engines are evaluated, and the results are used for an engine selection based on a simplified eVTOL mission capability.
Findings
By operating with high turbine inlet temperature, variable output speed and adequately sized recuperator, a turbogenerator provides exceptional efficiency at both nominal power and part load operation for a turbomachine, while maintaining the high power density required for aircraft. In application with a high peak-to-cruise power ratio, such power source would provide eight times the range of battery-electric power pack and an 80% improvement over the state-of-the-art simple cycle turbogenerator.
Practical implications
The implementation of a recuperator would provide additional gains especially important for military and on-demand mobility applications, notably reducing the heat signature and noise of the system. The engine low-pressure ratio reduces its complexity and combined with the fuel savings, the system could significantly reduce operational cost.
Originality/value
Implementation of radically new ICT architecture provides the key element to make a sub-megawatt recuperated turbogenerator viable in terms of power density. The synergetic combination of a recuperator, high temperature turbine and variable speed electric generator provides drastic improvement over simple-cycle turbines, making such a system highly relevant as the power source for future eVTOL applications.
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Keywords
Amir S. Gohardani and Omid Gohardani
The purpose of this paper is to outline the potential usage of ceramic engines in combination with other technologies as a possible propulsion contender for future aerospace…
Abstract
Purpose
The purpose of this paper is to outline the potential usage of ceramic engines in combination with other technologies as a possible propulsion contender for future aerospace applications.
Design/methodology/approach
The possibility of enabling novel propulsion systems in aerospace engineering is examined through a multilateral review study concerning ceramic engines and a proposed design approach. In view of the benefits and challenges of employing ceramic engines as possible candidates for the sustainable solutions of the future, a fundamental design proposal is presented for a conceptual generic unmanned air vehicle (GUAV).
Findings
The findings of this article identify a number of useful scenarios for future ceramic engine applications and considerations.
Research limitations/implications
It is imperative to emphasize that this conceptual article solely sheds light on a limited number of key ideas associated with ceramic engines and their possible applications. Thus, many new areas may emerge and impact the application of ceramic engines in light of more in‐depth conceptual studies.
Practical implications
Implications of ceramic engine utilization in aeronautical applications may result in enhanced performance characteristics and less operational costs. Further implications could possibly be extended to various naval/automotive applications and new configurations of transportation vehicles.
Social implications
The paper aims to generate an interest amongst younger individuals and environmental aware enthusiasts to consider ceramic engines for transportation applications to a greater extent than before.
Originality/value
The implementation of this particular conceptual design results in a synergistic ceramic engine combination with a hybrid airship design in novel aeronautical applications.
Details
Keywords
Mica Grujicic, S. Ramaswami and Jennifer Snipes
Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form…
Abstract
Purpose
Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using techniques such as the rule of mixtures. Given these properties, a composite armor the structure of which mimics that of nacre may have improved performance over a monolithic armor having a similar composition and an identical areal density. The paper aims to discuss these issues.
Design/methodology/approach
In the present work, an attempt is made to model a nacre-like composite armor consisting of B4C tablets and polyurea tablet/tablet interfaces. The armor is next tested with respect to impact by a solid right circular cylindrical (SRCC) rigid projectile, using a transient non-linear dynamics finite-element analysis. The ballistic-impact response and the penetration resistance of the armor are then compared with that of the B4C monolithic armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g. surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers, and B4C nano-crystallinity) on the ballistic-penetration resistance of the composite armor is investigated in order to identify an optimal nacre-like composite armor architecture having the largest penetration resistance.
Findings
The results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor-penetration resistance.
Originality/value
The present work indicates that for a given choice of armor material, penetration resistance may be improved by choosing a structure resembling that of nacre.
Details
Keywords
Mica Grujicic, Jennifer Snipes and S. Ramaswami
The purpose of this paper is to model a nacre-like composite material, consisting of tablets and polyurea tablet/tablet interfaces, B4C. This composite material is being…
Abstract
Purpose
The purpose of this paper is to model a nacre-like composite material, consisting of tablets and polyurea tablet/tablet interfaces, B4C. This composite material is being considered in the construction of the so-called backing-plate, a layer within a multi-functional/multi-layer armor system.
Design/methodology/approach
Considering the basic functions of the backing-plate (i.e. to provide structural support for the ceramic-strike-face and to stop a high-velocity projectile and the accompanying fragments) in such an armor system, the composite-material architecture is optimized with respect to simultaneously achieving high flexural stiffness and high ballistic-penetration resistance. Flexural stiffness and penetration resistance, for a given architecture of the nacre-like composite material, are assessed using a series of transient non-linear dynamics finite-element analyses. The suitability of the optimized composite material for use in backing-plate applications is then evaluated by comparing its performance against that of the rolled homogeneous armor (RHA), a common choice for the backing-plate material.
Findings
The results obtained established: a trade-off between the requirements for a high flexural stiffness and a high ballistic-penetration resistance in the nacre-like composite material; and overall superiority of the subject composite material over the RHA when used in the construction of the backing-plate within multi-functional/multi-layer armor systems.
Originality/value
This study extends the authors previous research on nacre-mimetic armor to optimize the architecture of the armor with respect to its flexural stiffness and ballistic-penetration resistance, so that these properties could be increased over the levels attained in the current choice (RHA) for the backing layer of multi-functional/multi-layer armor.
Details