Ceramic Composite Tubes Research Articles

Codes and standards for ceramic composite core materials for High Temperature Reactor applications

Fiber-reinforced ceramic matrix composites are attractive for high-temperature nuclear applications due to excellent thermal and mechanical properties as well as reasonable-to-outstanding radiation resistance. Over the past 20 years, the use of ceramic matrix composite applications expanded to many commercial non-nuclear industries as fabrication and application of the technologies mature.The ASME Boiler Pressure Vessel Code, under Section III Division 5, provides the design and construction rules for High Temperature Reactor components. It published the first rules for ceramic matrix composites to be used for reactor core components. The rules lay out the quality requirements together with the design and materials criteria for the use and application of silicon carbide- and carbon-based matrix material technologies. As with the established graphite rules, the ceramic composite material rules are structured in Subsection HH (from Section III), that addresses the criteria for class SN nonmetallic core components. The code rules rely heavily on the development and publication of standards for composite specification, classification, and testing of mechanical, thermal, and other properties. These test methods are developed in ASTM Committee C28 on Advanced Ceramics, with a current focus on ceramic composite tubes. This article describes the detail of the composites code, the design methodology and similarities to the graphite code, the guidance for the development of specifications for ceramic composites (for nuclear applications) including recent standard developments, and it mentions the next steps to support licensing aspects by validating the code with benchmarking data.

Hoop Strain Measurement During a SiC/SiC Ceramic Composite Tube Burst Test by Digital Volume Correlation of X-Ray Computed Tomographs

BackgroundSilicon carbide-fibre/silicon carbide matrix (SiC/SiC) composites are candidate materials for accident tolerant fuel cladding in light water and advanced gas cooled nuclear fission reactors. The mechanical and damage behaviour of ceramic composites is sensitive to the composite geometry, the microstructure and the loading state. Reliable test methods are needed to investigate the subcritical damage that affects hermetic properties and strength, and this requires precise measurements under loading states that are representative of operating conditions.ObjectiveThe objective was a novel methodology to measure the deformation of an internally pressurised ceramic composite tube.MethodsA burst test of an internally ground SiC/SiC (filament wound and braided) ceramic composite tube, pressurized by radial expansion of a compressed elastomer insert, was observed in situ by high resolution (synchrotron) X-ray tomography. The full field three-dimensional displacements were measured by digital volume correlation, with a precise rotation correction applied to obtain the relative radial and circumferential displacements of the tube wall for the first time.ResultsThe hoop strain, and its spatial variations, were determined as a function of the applied hoop stress and showed ovalisation and barreling of the tube. The quantity of subcritical matrix cracking increased with the tensile hoop strain, but the critical crack that caused rupture was not at the location of maximum tensile strain.ConclusionPrecise measurements of the deformation during the burst test found non-uniform hoop strains that caused a non-uniform distribution of subcritical cracking, which could influence the hermetic properties and strength.

ASME Code Rules and ASTM Standards Integration for Ceramic Composite Core Materials and Components1

Fiber-reinforced ceramic matrix composites have many desirable properties for high-temperature nuclear applications, including excellent thermal and mechanical properties and reasonable to outstanding radiation resistance. Over the last 20 years, the use of ceramic composite materials has already expanded in many commercial nonnuclear industries as fabrication and application technologies mature. The new ASME design and construction rules under Section III, Subsection HH, Subpart B lay out the requirements and criteria for materials, design, machining and installation, inspection, examination, testing, and the marking procedure for ceramic composite core components, which is similar to the established graphite code under Section III, Subsection HH, Subpart A. Moreover, the general requirements listed in Section III, Subsection HA, Subpart B are also expanded to include ceramic composite materials. The code rules rely heavily on the development and publication of standards for composite specification, classification, and testing of mechanical, thermal, and other properties. These test methods are developed in the American Society for Testing and Materials Committee C28 on Advanced Ceramics with a current focus on ceramic composite tubes. Details of the composites code, design methodology, and similarities to the graphite code, as well as guidance for the development of specifications for ceramic composites for nuclear application and recent standard developments, are discussed. The next step is to “close the gap” to support licensing aspects by validating the code with benchmarking data.

Enhanced filtration performance of Al2O3-SiC porous ceramic composite tube depending on microstructure and surface properties

Enhanced filtration performance of Al2O3-SiC porous ceramic composite tube depending on microstructure and surface properties

Near Net Shape Fabrication of Ceramic Composite Tube by Thermal Spray Forming

In the present study, a comparison has made between a prepared pure alumina tube and ceramic composite tubes fabricated by spray forming method with wall thickness of 1-2 mm and the diameter of 8-10 mm. Alumina with 5, 10, 15 and 20% of SiO2, Zirconia silicate with 5, 10, 15 and 20% of Al2O3 and Zirconia silicate with 5, 10, 15 and 20% of TiO2 have been fabricated. A detailed characterization of the spray-formed Al2O3 structure has performed using XRD, SEM, AFM and microhardness measurements. This study proved that a variety of structured materials and their combinations can be fabricated to near net shapes.

Scalable measurements of tow architecture variability in braided ceramic composite tubes

AbstractThe performance of braided ceramic matrix composites has been shown to depend on the spatial arrangement of tows; therefore, a new class of tools is required to measure irregularities in the composite architecture for components with intricate geometries. We report a scalable and robust reconstruction technique built upon stereoscopic digital image correlation that is able to efficiently measure the position of tows in arbitrarily shaped composites. This method was applied to triaxially braided ceramic matrix composite tubes intended for use as nuclear fuel cladding, which revealed both long‐range “systematic” tow packing defects associated with the manufacturing process and short‐range “intrinsic” defects due to the braid architecture. These findings suggested that the character of tow spacing variation in braided composite tubes was substantially more complex than in planar woven composites. These measurements are expected to lead to improved processing of braided composites and to facilitate the design of statistically representative virtual specimens for finite element modeling.

In situ observation of mechanical damage within a SiC-SiC ceramic matrix composite

SiC-SiC ceramic matrix composites are candidate materials for fuel cladding in Generation IV nuclear fission reactors and as accident tolerant fuel clad in current generation plant. Experimental methods are needed that can detect and quantify the development of mechanical damage, to support modelling and qualification tests for these critical components. In situ observations of damage development have been obtained of tensile and C-ring mechanical test specimens of a braided nuclear grade SiC-SiC ceramic composite tube, using a combination of ex situ and in situ computed X-ray tomography observation and digital volume correlation analysis. The gradual development of damage by matrix cracking and also the influence of non-uniform loading are examined.

Multi-scale damage modelling in a ceramic matrix composite using a finite-element microstructure meshfree methodology.

The problem of multi-scale modelling of damage development in a SiC ceramic fibre-reinforced SiC matrix ceramic composite tube is addressed, with the objective of demonstrating the ability of the finite-element microstructure meshfree (FEMME) model to introduce important aspects of the microstructure into a larger scale model of the component. These are particularly the location, orientation and geometry of significant porosity and the load-carrying capability and quasi-brittle failure behaviour of the fibre tows. The FEMME model uses finite-element and cellular automata layers, connected by a meshfree layer, to efficiently couple the damage in the microstructure with the strain field at the component level. Comparison is made with experimental observations of damage development in an axially loaded composite tube, studied by X-ray computed tomography and digital volume correlation. Recommendations are made for further development of the model to achieve greater fidelity to the microstructure. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

FABRICATION AND MATERIAL ISSUES FOR THE APPLICATION OF SiC COMPOSITES TO LWR FUEL CLADDING

The fabrication methods and requirements of the fiber, interphase, and matrix of nuclear grade SiC f /SiC composites are briefly reviewed. A CVI-processed SiC f /SiC composite with a PyC or (PyC-SiC)n interphase utilizing Hi-Nicalon Type S or Tyranno SA3 fiber is currently the best combination in terms of the irradiation performance. We also describe important material issues for the application of SiC composites to LWR fuel cladding. The kinetics of the SiC corrosion under LWR conditions needs to be clarified to confirm the possibility of a burn-up extension and the cost-benefit effect of the SiC composite cladding. In addition, the development of end-plug joining technology and fission products retention capability of the ceramic composite tube would be key challenges for the successful application of SiC composite cladding.

Fabrication and testing of all-oxide CFCC tubes

A novel, low-cost processing method was used to manufacture all-oxide ceramic composite tubes. Fibre cloths were infiltrated with a pre-consolidated slurry composed of a mixture of mullite and alumina powders. The pre-consolidated slurry was first formulated at a low volume fraction of powder to produce a short-range repulsive interparticle pair potential that allowed consolidation via pressure filtration, yet produced a consolidated body that could be fluidised by vibration. Efficient infiltration of fibre tows and a homogeneous microstructure were demonstrated. The infiltrated cloths, which could be frozen for latter use, were rolled to tubular shapes. After drying, the powder matrix was strengthened by cyclic infiltration and pyrolysis of an alumina precursor. When the tubes were pressurised, they delaminated at an average hoop stress of 47 MPa. Delamination initiated within the porous matrix where the outer most layer terminated. A failure analysis is presented using a strain energy release rate function for this specimen/crack configuration. Values of fracture energy inferred from the analysis were in close agreement with literature data for porous ceramics.

Failure of a continuous fiber ceramic composite after exposure to combustion ambients

A forensic investigation was performed to understand the failure of a continuous fiber ceramic composite tube used in a slot-forge furnace. The failure study consisted of visual inspections of both failed shards and as-received samples taken from a section removed before the tube was placed in service. Semi-quantitative SEM, X-ray diffraction, and microstructural analyses were also performed to determine the nature of glazing observed on the surface of the failed tube. Based on this analysis, the failure was apparently caused by oxidation and an eventual “burn-through and collapse” that was most likely precipitated by significant temperature excursions in excess of 1427 °C.

Electrophoretic Forming of Laminated Ceramic Composite Tubes

Electrophoretic Forming of Laminated Ceramic Composite Tubes

CVI/CVD for SiC Composites

Ceramic composite components in a wide variety of shapes have been fabricated by a combination of chemical vapor infiltration (CVI) and chemical vapor deposition (CVD) of silicon carbide. Continuous Nextel and Nicalon ceramic fibers, which were woven into cloth, have been used as substrates for these depositions. Ceramic composite tubes and baskets as well as corrugated and flat panels have been fabricated by infiltrating and depositing approximately 0.08 cm of silicon carbide on the cloth substrates. By varying the weave architecture and regulating the deposition time, the porosity can be changed from open to vacuum tight.