High Temperature Fatigue Assessment of a SiCf/SiC Ceramic Matrix Composite Using Advanced Monitoring Techniques

2019 ◽  
Author(s):  
Christopher D. Newton ◽  
Steven P. Jordan ◽  
Martin R. Bache ◽  
Louise Gale
Keyword(s):  
Silicon Carbide ◽  
Crack Opening ◽  
Ceramic Matrix Composite ◽  
Fatigue Loading ◽  
Cyclic Stress ◽  
Image Correlation ◽  
Material System ◽  
Damage Initiation ◽  
Macro Scale ◽  
Stress States

Abstract Laboratory based experiments to assess the “damage tolerance” of any new material system are a pre-requisite to engineering design, especially for aerospace components. In the case of CMCs, macro-scale specimens are preferred containing representative fibre-matrix architectures that support the definition of mechanical properties under service representative stress states. The combination of complex internal structure and inevitable processing artefacts within CMCs provides numerous sites for damage initiation. Damage then progresses in an inhomogeneous manner prior to ultimate failure at some critical location. Traditional techniques employed for strain measurement (extensometry/strain gauges) prove to be ineffective tools when testing these advanced composites. More complex characterization is essential in order to assess the localised response of the material. Advanced techniques, specifically digital image correlation and acoustic emission, have been applied to the evaluation of an CVI/MI silicon carbide reinforced/silicon carbide CMC tested at the elevated temperature of 800°C under fatigue loading. The spatial and temporal indications of damage were correlated to the observable forms of damage initiation and progression. Ancillary use of an in-situ SEM loading stage provided insight into the crack opening and closing mechanisms active within this material when under cyclic stress.

scholarly journals Advances in Damage Monitoring Techniques for the Detection of Failure in SiCf/SiC Ceramic Matrix Composites

Ceramics ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 347-371 ◽  
Author(s):  
Martin R. Bache ◽  
Christopher D. Newton ◽  
John Paul Jones ◽  
Stephen Pattison ◽  
Louise Gale ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Loading ◽  
Industrial Applications ◽  
Image Correlation ◽  
Full Potential ◽  
Matrix Composites ◽  
Monitoring Techniques ◽  
Macro Scale

From a disruptive perspective, silicon carbide (SiC)-based ceramic matrix composites (CMCs) provide a considerable temperature and weight advantage over existing material systems and are increasingly finding application in aerospace, power generation and high-end automotive industries. The complex structural architecture and inherent processing artefacts within CMCs combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in CMCs. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. This is important if CMCs are to be utilised to their full potential within industrial applications. Bulk measurements of strain via extensometry or even localised strain gauging would fail to characterise the ensuing inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high-temperature assessment of ceramic matrix composites under axial tensile and fatigue loading, with particular attention afforded to a silicon carbide fibre-reinforced silicon carbide composite (SiCf/SiC) variant. Data from these separate monitoring techniques plus ancillary use of X-ray computed tomography, in-situ scanning electron microscopy and optical inspection were correlated to monitor the onset and progression of damage during mechanical loading. The benefits of employing a concurrent, multi-technique approach to monitoring damage in CMCs are demonstrated.

High Temperature Solid Particle Erosion in a Melt-Infiltrated SiC/SiC Ceramic Matrix Composite

2021 ◽  
Author(s):  
Michael J. Presby
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Gas Turbines ◽  
Material Removal ◽  
Gas Flow ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Solid Particles ◽  
Material System

Abstract Ceramic matrix composites (CMCs) are an enabling propulsion material system that offer weight benefits over current Ni-based superalloys, and have higher temperature capabilities that can reduce cooling requirements. Incorporating CMCs into the hot section of gas-turbine engines therefore leads to an increase in engine efficiency. While significant advancements have been made, challenges still remain for current and next-generation gas-turbines; particularly when operating in dust-laden or erosive environments. Solid particles entrained in the gas flow can impact engine hardware resulting in localized damage and material removal due to repeated, cumulative impacts. In this study, the erosion behavior of a melt-infiltrated (MI) silicon carbide fiber-reinforced silicon carbide (SiC/SiC) CMC is investigated at high temperature (1,200 °C) in a simulated combustion environment using 150 μm alumina particles as erodent. Particle impact velocities ranged from 100 to 200 m/s and the angle of impingement varied from 30° to 90°. Erosion testing was also performed on α-SiC to elucidate similarities and differences in the erosion response of the composite compared to that of a monolithic ceramic. Scanning electron microscopy (SEM) was used to study the post-erosion damage morphology and the governing mechanisms of material removal.

Detection of Strain and Damage Distribution in SiCf/SiC Mechanical Test Coupons

2018 ◽  
Author(s):  
Christopher D. Newton ◽  
J. Paul Jones ◽  
Louise Gale ◽  
Martin R. Bache
Keyword(s):  
Mechanical Test ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Loading ◽  
Image Correlation ◽  
Matrix Composites ◽  
Macro Scale ◽  
Ultimate Failure ◽  
Complex Structural ◽  
Structural Architecture

The complex structural architecture and inherent processing artefacts within ceramic matrix composites combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. Bulk measurements of strain via extensometry or even localised strain gauging will fail to characterise such inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research project has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high temperature assessment of a SiCf/SiC composite under axial fatigue loading. Data from these separate monitoring techniques plus ancillary use of X-Ray computed tomography and optical inspection were correlated to monitor the onset and progression of damage during cyclic loading.

scholarly journals Dynamic fracture of a dual phase automotive steel

2018 ◽  
Vol 183 ◽  
pp. 02047
Author(s):  
Sarath Chandran ◽  
Patricia Verleysen ◽  
Junhe Lian ◽  
Wenqi Liu ◽  
Sebastian Münstermann
Keyword(s):  
High Strain ◽  
Image Correlation ◽  
Fracture Mechanisms ◽  
Dual Phase ◽  
Strain Rates ◽  
High Strain Rates ◽  
Damage Initiation ◽  
Damage And Fracture ◽  
Wide Range ◽  
Stress States

Dynamic testing of sheet metals has become more important due to the need for more reliable vehicle crashworthiness assessments in the automotive industry. The study presents a comprehensive set of experimental results that covers a wide range of stress states on a dual phase automotive sheet steel. Split Hopkinson bar tensile (SHBT) tests are performed on dogbone shaped samples to obtain the plastic hardening properties at high strain rates. A set of purpose designed sample geometries comprising of three notched dogbone tension samples is tested at high strain rates to characterise the dynamic damage and fracture properties under well controlled stress states. The geometry of the samples is optimised with the aid of finite element analysis. During the tests, high speed photography together with digital image correlation are implemented to acquire full field measurements and to gain more insight into the localisation of strains at high strain rates. An experimental-numerical approach is proposed to effectively determine the fracture characteristics of the dual phase steel under extreme conditions. A modified Bai-Wierzbicki model is implemented to assess the damage initiation and subsequent failure. Additionally, the fracture mechanisms are studied utilizing scanning electron microscopy.

High Temperature Solid Particle Erosion in a Melt-Infiltrated SiC/SiC Ceramic Matrix Composite

2021 ◽  
Author(s):  
Michael Presby
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Gas Turbines ◽  
Material Removal ◽  
Gas Flow ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Solid Particles ◽  
Material System

Abstract Ceramic matrix composites (CMCs) are an enabling propulsion material system that offer weight benefits over current Ni-based superalloys, and have higher temperature capabilities that can reduce cooling requirements. Incorporating CMCs into the hot section of gas-turbine engines therefore leads to an increase in engine efficiency. While significant advancements have been made, challenges still remain for current and next-generation gas-turbines; particularly when operating in dust-laden or erosive environments. Solid particles entrained in the gas flow can impact engine hardware resulting in localized damage and material removal due to repeated, cumulative impacts. In this study, the erosion behavior of a melt-infiltrated (MI) silicon carbide fiber-reinforced silicon carbide (SiC/SiC) CMC is investigated at high temperature (1,200 °C) in a simulated combustion environment using 150 µm alumina particles as erodent. Particle impact velocities ranged from 100 to 200 m/s and the angle of impingement varied from 30° to 90°. Erosion testing was also performed on a-SiC to elucidate similarities and differences in the erosion response of the composite compared to that of a monolithic ceramic. Scanning electron microscopy (SEM) was used to study the post-erosion damage morphology and the governing mechanisms of material removal.

scholarly journals Use of the AE Effect to Determine the Stresses State in AAC Masonry Walls under Compression

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3459
Author(s):  
Radosław Jasiński ◽  
Krzysztof Stebel ◽  
Paweł Kielan
Keyword(s):  
Ultrasonic Waves ◽  
Image Correlation ◽  
Masonry Walls ◽  
Acceptable Error ◽  
Compressive Stresses ◽  
Deformation State ◽  
Hydrostatic Stresses ◽  
Stress States ◽  
The Impact ◽  
Masonry Units

Safety and reliability of constructions operated are predicted using the known mechanical properties of materials and geometry of cross-sections, and also the known internal forces. The extensometry technique (electro-resistant tensometers, wire gauges, sensor systems) is a common method applied under laboratory conditions to determine the deformation state of a material. The construction sector rarely uses ultrasonic extensometry with the acoustoelastic (AE) method which is based on the relation between the direction of ultrasonic waves and the direction of normal stresses. It is generally used to identify stress states of machine or vehicles parts, mainly made of steel, characterized by high homogeneity and a lack of inherent internal defects. The AE effect was detected in autoclaved aerated concrete (AAC), which is usually used in masonry units. The acoustoelastic effect was used in the tests described to identify the complex stress state in masonry walls (masonry units) made of AAC. At first, the relationships were determined for mean hydrostatic stresses P and mean compressive stresses σ3 with relation to velocities of the longitudinal ultrasonic wave cp. These stresses were used to determine stresses σ3. The discrete approach was used which consists in analyzing single masonry units. Changes in velocity of longitudinal waves were identified at a test stand to control the stress states of an element tested by the digital image correlation (DIC) technique. The analyses involved density and the impact of moisture content of AAC. Then, the method was verified on nine walls subjected to axial compression and the model was validated with the FEM micromodel. It was demonstrated that mean compressive stresses σ3 and hydrostatic stresses, which were determined for the masonry using the method considered, could be determined even up to ca. 75% of failure stresses at the acceptable error level of 15%. Stresses σ1 parallel to bed joints were calculated using the known mean hydrostatic stresses and mean compressive stresses σ3.

Damage Development in SiCf/SiC Composites Through Mechanical Loading

2017 ◽  
Author(s):  
Martin R. Bache ◽  
J. Paul Jones ◽  
Zak Quiney ◽  
Louise Gale
Keyword(s):  
Acoustic Emission ◽  
Mechanical Loading ◽  
Ceramic Matrix Composites ◽  
Potential Drop ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Damage Development ◽  
Macro Scale ◽  
Sic Composites ◽  
The Individual

Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in ceramic matrix composites. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. Standard SiCf/SiC processing techniques inherently introduce porosity between the individual reinforcing fibres and between woven fibre bundles. Subsequent mechanical loading (static or cyclic) may initiate cracking from these stress concentrations in addition to fibre/matrix decohesion and delamination. The localised coalescence of such damage ultimately leads to rapid failure. Proven techniques for the monitoring of damage in structural metallics, i.e. optical microscopy, potential drop systems, acoustic emission (AE) and digital image correlation (DIC), have been adapted for the characterisation of CMC’s tested at room temperature. As processed SiCf/SiC panels were subjected to detailed X-ray computed tomography (XCT) inspection prior to specimen extraction and subsequent static and cyclic mechanical testing to verify their condition. DIC strain measurements, acoustic emission and resistance monitoring were performed and correlated to monitor the onset of damage during loading, followed by intermittent XCT inspections throughout the course of selected tests.

scholarly journals Modeling of Bimodular Bone Specimen under Four-Point Bending Fatigue Loading

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 474
Author(s):  
Yufan Yan ◽  
Xianjia Meng ◽  
Chuanyong Qu
Keyword(s):  
Compressive Strain ◽  
Fatigue Loading ◽  
Degradation Process ◽  
Neutral Axis ◽  
Image Correlation ◽  
Bending Test ◽  
Correlation Technique ◽  
Fatigue Process ◽  
Four Point Bending ◽  
Bone Properties

The fatigue damage behavior of bone has attracted significant attention in both the mechanical and orthopedic fields. However, due to the complex and hierarchical structure of bone, describing the damage process quantitively or qualitatively is still a significant challenge for researchers in this area. In this study, a nonlinear bi-modulus gradient model was proposed to quantify the neutral axis skewing under fatigue load in a four-point bending test. The digital image correlation technique was used to analyze the tensile and compressive strains during the fatigue process. The results showed that the compressive strain demonstrated an obvious two-stage ascending behavior, whereas the tensile strain revealed a slow upward progression during the fatigue process. Subsequently, a theoretical model was proposed to describe the degradation process of the elastic modulus and the movement of the neutral axis. The changes in the bone properties were determined using the FEM method based on the newly developed model. The results obtained from two different methods exhibited a good degree of consistency. The results obtained in this study are of help in terms of effectively exploring the damage evolution of the bone materials.

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