Mechanical behavior of 2.5D (shallow straight-joint) and 3D four-directional braided SiO2f/SiO2 composites

The effect of two different fiber architectures on the mechanical properties and mechanical behavior of the SiO2f/SiO2 composites processed by silicasol-infiltration-sintering has been investigated. The composites were sintered at relatively low temperature (450 degrees C). The fiber/matrix interface strength was weak. The characteristics of 2.5D (shallow straight-joint) structure and 3D four-directional braided structure were determined. The tensile strength, flexural strength, shear strength and failure mechanisms of both 2.5D (shallow straight-joint) and 3D four-directional braided SiO2f/SiO2 composites were characterized. It was found that the fiber placement in the preform will strongly affect the mechanical property and failure behavior of the composite. The results of the tests and microstructural observations indicated that 3D four-directional braided SiO2f/SiO2 composite had better mechanical properties than 2.5D (shallow straight-joint) SiO2f/SiO2 composite. 3D four-directional braided SiO2f/SiO2 composite exhibited more graceful failure under loading than 2.5D (shallow straight-joint) SiO2f/SiO2 composite. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.