In situ Observation of Compression Damage in a Three-Dimensional Braided Carbon Fiber Reinforced Carbon and Silicon Carbide (C/C-SiC) Ceramic Composite

Abstract

Deformation and mechanical damage in a three-dimensional braided carbon fiber reinforced carbon and silicon carbide ceramic composite, subjected to compressive loading, has been studied in situ by laboratory X-ray computed tomography. Dimensional change was measured and damage visualized by digital volume correlation analysis of tomographs. Cracks nucleated from defects within the fiber bundles and tended to propagate along the fiber bundle/matrix interface. For longitudinal compression, parallel to the fiber bundles, the initial elastic modulus decreased with increasing compressive strain while significant transverse tensile strains developed due to distributed cracking. For transverse compression, perpendicular to the fiber bundles, the compressive elastic modulus was effectively constant; the tensile strains developed along the fiber direction were small, whereas macroscopic fracture between the fiber bundles caused very large bulk tensile strain perpendicular to the loading. The observations suggest that the mechanical strength might be improved through control of pre-existing defects and application of stitch fibers in the transverse direction.

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

“…The fracture surfaces from the tests performed at 800 • C also demonstrated more restricted fibre pull out. This behaviour is consistent with a reduction in crack density with increased temperature reported for a range of SiC matrix CMC systems, notably incorporating various classes of fibre and interface phase [15,18] and has been attributed to a moderate reduction in brittle behaviour.…”

“…In-situ SEM studies provide excellent resolution of surface crack opening and closure; however, the field of view is highly restricted. It may be argued that continuous synchrotron X-ray computed tomography be considered as the ultimate technique available for the resolution of damage within a reasonably large volume of CMC material [15]; however, access to beam-line facilities with in-situ loading is restrictive. When looking ahead to the service inspection of CMC components, some form of ER or mechanical resonance technique may be favoured for condition monitoring, especially if the part has to remain in-situ within a supporting structure.…”

X-ray tomography of additive-manufactured zirconia: Processing defects – Strength relations

“…Particular interest has been recently shown for the application of XCT in the field of AM, to evaluate AM methods, to control the geometry of the produced components or to characterize their microstructure [33][34][35][36][37]. In the field of ceramic materials, XCT have been particularly used for structural or damage characterization of ceramic matrix composites [38][39][40][41][42][43] and to evaluate pore morphology and interconnectivity of porous or cellular ceramics [44][45][46][47][48][49][50]. XCT analysis was also applied to follow the microstructural evolutions during the compaction process of [51] or their sintering [52][53][54], and to investigate indentation induced cracking in dense alumina [55].…”

Microstructure Characterization by X-Ray Computed Tomography of C/C-SiC Ceramic Composites Fabricated with Different Carbon Fiber Architectures

“…However, intra-bundle pores that are in the carbon preform, which may be closed or open, can be detrimental to material performance. Closed intra-bundle pores can initiate cracks under mechanical loading [25], while open intra-bundle pores, which may be continuous, will act as a transport path for oxidation and may offset the beneficial effects of SiC to ablation resistance [37]. The microstructure characteristics and the proportion and distribution of open pores in architecture ③ indicate that it would be expected to have better oxidation-resistance than architectures ① and ②.…”

“…Consequently, XCT as an advanced non-destructive technique has been applied to a wide range of materials, including wood [13], concrete [14], gypsum [15], graphite [16,17] and polymer composites [18]. Various ceramic matrix composites [19][20][21][22][23] have also been investigated, but only a few studies have examined C/C-SiC composites [24][25][26][27].…”