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

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.

Volumetric assessment of fatigue damage in a SiCf/SiC ceramic matrix composite via in situ X-ray computed tomography

“…Identical test conditions to those applied to the in situ fatigue tests reported above were employed on a CMC coupon of the same CMC variant but loaded in a standard laboratory test rig. As previously published [7], AE sensors were interfaced to the specimen and the onset of damage accumulation monitored as a function of cycles, Figure 8. A distinct and immediate increase in accumulated AE energy was recorded during the first load cycle.…”

“…Other authors have used synchrotron radiation sources to acquire higher resolution in situ XCT images of CMCs [5,6], but this adversely restricts the available field of view to the microscale. In situ digital image correlation (DIC) and scanning electron microscope (SEM) imaging techniques have also been demonstrated [7], but are restricted to surface measurements. Visually, XCT provides an unrivalled depiction of damage within the internal structure of a CMC, however, it can be difficult to obtain quantifiable measurements of overall damage from the analysis.…”

Review of microwave techniques used in the manufacture and fault detection of aircraft composites

“…Liquid-coupled ultrasonics can be used for inspection of internal defects/damage, and couplants (water or gels) are usually needed. There is ongoing research on other non-destructive testing (NDT) techniques for more accurate evaluation and convenient implementation, such as acoustic emission (2-8) , guided waves (9-18) (e.g. piezoelectric transducer-based (19,20) and angle beam transducer-based (21,22) ), air-coupled ultrasonics (23-30) , thermography (31-36) , optical fibre sensing (37-42) , digital image correlation (DIC) (43-48) , electromagnetic testing (49-51) (e.g.…”

A time-dependent tensile constitutive model for long-fiber-reinforced unidirectional ceramic-matrix minicomposites considering interface and fiber oxidation

“…The mechanical properties reflect the damage resistance of composites under different loading conditions, which is an important index for the safety design of components (Baranger, 2013; Chen et al., 2007; Christopher and Choudhary, 2019; Marcin et al., 2011). It is directly related to the safety and reliability of components in service and the predictability of damage (Bache et al., 2019; Baranger, 2019; Mareau and Morel, 2019; Matta et al., 2019; Yu et al., 2019). The tensile stress–strain behavior reflects the strength of the composite material to resist the damage of external tensile loading.…”