Papers by Author: Hui Mei

Abstract: The electrospun nanofiber/graphene composites is a promising candidate in the field of flexible strain sensors due to the synergic effect of graphene and the nanofibers. It is an effective way to synthesize a uniform graphene-embedded film by simultaneously electrospinning nanofibers and electrospraying graphene nanosheets. In this paper, we prepare two specimens of different materials to study the interaction between graphene nanosheets and nanofibers under the same process parameters, such as thermoplastic urethane (TPU), polyacrylonitrile (PAN). Then, morphology and mechanical properties are used to characterize the interaction. The mechanical test was conducted by the tensile tester, and the surface morphology of electrospun nanofibrous films was observed through a microscope. By comparing these results, the properties of the graphene nanosheets embedded to different nanofibers are explored. This study provides a good way to select an appropriate nanofiber matrix for the application in flexible strain sensors.

Abstract: Three-dimensional (3D) carbon fiber reinforced silicon carbide matrix composites (C/SiC) were prepared by a low-pressure chemical vapor infiltration method. The thermal shock behaviors of the composites in different environments were researched using an advanced acoustic emission (AE) system. Damage initiation and propagation were easily detected and evaluated by AE. The thermal shock damage to C/SiC composites mainly occurred at the process of cooling and was limited at argon but unlimited at wet oxygen atmosphere. Also correlations have been established between the different damage mechanisms and the characteristics of acoustic emission signals obtained during thermal shock tests. In this way, the paper contributes to the development of the acoustic emission technique for monitoring of damage development in ceramic-matrix composites.

Abstract: The conventional ultimate performance test by applying a component in its true application (i.e., in an engine) is often very expensive and impractical when dealing with developmental materials. Simpler, less expensive, and more practical test methods must be utilized. The present work aims toward the applications of an innovative methodology for testing environmental performance of advanced Ceramic Matrix Composites (CMCs) in the presence of combined mechanical, thermal, and environmental applied conditions. To obtain a comprehensive understanding of how a composite might perform in certain application environments, a newly developed environmental performance testing system, which is able to provide the fundamental damage information of the composites in simulating service environments including variables such as temperature, mechanical and thermal stresses, flowing oxidizing gases and high gas pressure, is proposed. The system comprises of two subsystems: (1) equivalent experimental simulating subsystem, and (2) wind tunnel experimental simulating subsystem. The evolution mechanisms of the composites properties and microstructures can be achieved by the former, and then be validated and modified by the latter. Various loading (e.g. fatigue, creep), various atmospheres (e.g. argon, oxygen, water vapor, wet oxygen and molten salt vapor) and various temperature conditions (e.g. constant or cyclic temperatures) can be conducted on the system. Some typical experimental results are presented in this paper. Large quantities of tests have demonstrated the extraordinary stability and reliability of the system.