Full-field characterisation of oxide-oxide ceramic-matrix composites using X-ray computed micro-tomography and digital volume correlation under load at high temperatures. (October 2021)

• Record Type: Journal Article
• Authors: Forna-Kreutzer, J. Paul; Ell, Jon; Barnard, Harold; Pirzada, Talha J.; Ritchie, Robert O.; Liu, Dong
• Is Part Of: Materials & design. Volume 208(2021)
• Publication Date: 2021-10
• Subjects: Oxide-oxide ceramic-matrix composites -- In situ full-field characterisation -- High-temperature X-ray computed micro-tomography -- Digital volume correlation -- Deformation and fracture; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2021.109899
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Higher sintering temperatures resulted in higher flexural failure strengths. Failure occurred through three primary cracking mechanisms in both materials. Pre-failure maximum principal strains were good predictors for fracture initiation. 3-D local microstructural strains revealed abrupt shear strain gradients. Abstract: In situ synchrotron X-ray computed micro-tomography and digital volume correlation (DVC) were utilised to understand the failure mechanisms at room temperature and 1050 °C of two Nextel™720/alumina oxide-oxide ceramic-matrix composites (CMCs), termed materials A and B, sintered respectively at 1200 °C and ~1250 °C. At both test temperatures, three-point-bending strengths were ~55–58 MPa for material A and ~94–100 MPa for material B. Damage was associated with three primary types of cracking modes: interfacial delamination, inclined cracks within fibre tows, opening of existing matrix shrinkage cracks. Material A exhibited higher shrinkage cracking, whereas material B displayed more pronounced diagonal matrix microcracking. At 1050 °C, both systems showed less microcracking but more pronounced delamination. Such damage characteristics were rationalised in terms of the corresponding 3D DVC displacement/strain fields. Specifically, global DVC was utilised and maximum principal strain locations prior to failure, which varied from 0.005 to 0.01, correlated well to the fracture initiation sites. Further, abrupt positive to negative transitions of shear strain components were observed and were attributed to the different bonding strengths between 0°/90° fibres and the matrix. The current study demonstrates that in situ high-temperature tomography/DVC is a powerful method for studying the deformation and fracture of oxide-oxide CMCs.