Abstract
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.
Highlights
Ceramic matrix composites (CMCs) offer a combination of low density and thermal stability for structural engineering applications where long-term exposure to high-temperature environments is envisaged
ceramic matrix composites (CMCs) made from woven silicon carbide (SiCf ) fibres embedded within a SiC matrix have shown the greatest promise for high-temperature application over extended periods in oxidising environments
The present paper describes tests on notched coupons subjected to axial stress, with real-time surface strain distributions measured via digital image correlation (DIC)
Summary
Ceramic matrix composites (CMCs) offer a combination of low density and thermal stability for structural engineering applications where long-term exposure to high-temperature environments is envisaged. Advanced processing techniques have been optimised to produce CMC materials based on oxide/oxide and silicon carbide fibre-reinforced silicon carbide composite (SiCf /SiC) systems, for example, which can be tailored to the manufacture of engineering components destined to Ceramics 2019, 2, 347–371; doi:10.3390/ceramics2020028 www.mdpi.com/journal/ceramics. CMCs made from woven silicon carbide (SiCf ) fibres embedded within a SiC matrix have shown the greatest promise for high-temperature application over extended periods in oxidising environments. Their beneficial properties include high-temperature strength, low density, resistance to thermal shock, improved toughness (relative to monolithic variants), good creep and corrosion resistance
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