Acoustic emission as a screening tool for ceramic matrix composites

Abstract

Ceramic matrix composites are composite materials with ceramic fibers in a high temperature matrix of ceramic or glass-ceramic. This emerging class of materials is viewed as enabling for efficiency improvements in many energy conversion systems. The key controlling property of ceramic matrix composites is a relatively weak interface between the matrix and the fiber that aids crack deflection and fiber pullout resulting in greatly increased toughness over monolithic ceramics. United Technologies Research Center has been investigating glass-ceramic composite systems as a tool to understand processing effects on material performance related to the performance of the weak interface. Changes in the interface have been shown to affect the mechanical performance observed in flexural testing and subsequent microstructural investigations have confirmed the performance (or lack thereof) of the interface coating. Recently, the addition of acoustic emission testing during flexural testing has aided the understanding of the characteristics of the interface and its performance. The acoustic emission onset stress changes with strength and toughness and this could be a quality tool in screening the material before further development and use. The results of testing and analysis will be shown and additional material from other ceramic matrix composite systems may be included to show trends.

Unveiling hermetic failure of ceramic tubes by digital image correlation and acoustic emission

“…Addressing this challenge, 3D‐DIC was leveraged to measure spatial strain fields over a targeted area of interest with sufficient resolution to track local strain concentrations associated with composite architectural features . AE monitoring was used to identify the strains at the onset and progression of cracking, leading to loss of He gas tightness . This work is intended to advance the scientific evaluation of brittle constituent tubes and progress the optimization of SiC/SiC CMCs for extreme conditions.…”

“…[23][24][25][26] AE monitoring was used to identify the strains at the onset and progression of cracking, leading to loss of He gas tightness. [27][28][29] This work is intended to advance the scientific evaluation of brittle constituent tubes and progress the optimization of SiC/SiC CMCs for extreme conditions. Table 1 lists the specifications of the four different materials tested, including outer diameter (OD) and inner diameter (ID).…”

Mechanical property and failure mechanism of coated Al2O3f/SiO2 composites by acoustic emission technology (AE)

“…In composites, the modulus mainly represented the matrix performance. 27,28 Therefore, the silicon oxide matrix was seriously damaged in the early stage of the short-beam shear test. By contrast, the sudden drop in the load in the shear test occurs without an appreciable change in modulus.…”

“…Therefore, AE technology is suitable for detecting damage in polymer matrix and CMC. 28,29 However, reports on the application of AE detection technology to OCMCs are few.…”

“…Compared with metal materials, the composites exhibit more complex response mechanisms under load compared with metal materials. Therefore, AE technology is suitable for detecting damage in polymer matrix and CMC 28,29 . However, reports on the application of AE detection technology to OCMCs are few.…”