Failure evaluation of neutron-irradiated SiC/SiC composites by underwater acoustic emission

Understanding the statistical properties of mechanical properties of non-irradiated and neutron-irradiated SiC/SiC composites is essential for component design. This study aims to evaluate the detailed damage accumulation behavior of composites focusing on two fracture parameters: proportional limit stress (PLS) and acoustic emission (AE) onset stress. The developmental underwater AE technique, which is benefit in non-contact in-situ failure monitoring method during mechanical testing and in handle of the irradiated material, was first applied to evaluate damage accumulation behavior. Two types of chemical vapor infiltration SiC/SiC composites were used: one reinforced with Hi-Nicalon Type-S SiC fiber and one reinforced with Tyranno-SA3 SiC fiber in the form of satin-woven 2D fabrics with pyrolytic carbon interface. Neutron irradiation in the High Flux Isotope Reactor at Oak Ridge National Laboratory reached a fluence of 30 dpa at a temperature of 620-670 C. Four-point flexural tests were conducted to evaluate post-irradiation strength. Weibull statistics did not suggest marked degradation of composite strength. Detailed failure behavior evaluated by AE demonstrated no irradiation-induced change of the AE onset stress (i.e., crack initiation equivalent stress). Failure probability analysis suggests that increasing the reliability of composites (i.e., the Weibull modulus rather than strength itself) is essential to expanding the design margin and benefiting from a probabilistic design approach. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Understanding the statistical properties of mechanical properties in non-irradiated and neutron-irradiated SiC/SiC composites is crucial for component design. This study evaluated the damage accumulation behavior of composites, focusing on fracture parameters such as proportional limit stress and acoustic emission onset stress. The study used underwater acoustic emission technique and conducted four-point flexural tests to evaluate the post-irradiation strength of two types of SiC/SiC composites. The results showed that the reliability of composites is crucial for expanding design margin and utilizing a probabilistic design approach.