Many important ceramics are ferroelastic, eg, lanthanum strontium manganate (LSM), which is used as a cathode in solid oxide fuel cells. The objective of the proposed research is to investigate the problem of fracture at notches in ferroelastic ceramics subjected to compressive loading. Ceramics are often preloaded in compression to avoid brittle failure. Preliminary work at QMUL on ferroelectric/ferroelastic ceramics has demonstrated that compression-compression loading of notches can produce fracture at a surprisingly small far-field stresses.
The results of this work have significant implications for the design and performance of ferroelastic materials containing fabricated or machined notched structures, such as solid oxide fuel cell components and interdigitated multi-layer ferroelectric ceramic actuators. The origin of the effect may be the relatively large strain irreversibility produced in ferroelastic ceramics and the tensile stresses that this can generate on unloading. We propose to investigate the factors (eg, notch geometry, peak load, load ratio, loading rate / frequency, and material properties) that influence fracture and to model the problem using finite element analysis. An important outcome of the work will be an improved knowledge of good design practice for ferroelastic ceramic components.
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