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In this paper, SiO2f/SiO2 composites reinforced by 3D four‐directional braided quartz preform were prepared by the silica sol‐infiltration‐sintering method in a relatively low sintering temperature (450 °C). To characterize the mechanical properties of the composites, mechanical testing was carried out under various loading conditions, including tensile, flexural and shear loading. The microstructure and the fracture behaviour of the 3D four‐directional braided SiO2f/SiO2 composites were studied. The tensile strength, flexural strength and the in‐plane shear strength were 30.8 MPa, 64.0 MPa and 22.0 MPa, respectively. The as‐fabricated composite exhibited highly nonlinear stress–strain behaviour under all the three types of loading. The tensile and flexural fracture mechanisms were fully discussed. The fracture mode of the 3D four‐directional braided SiO2f/SiO2 composite in the Iosipescu shear testing was based on a mixed mechanism because of the multi‐directivity of the composite. Owing to low sintered temperature, the fibre/matrix interfacial strength was weak. The SiO2f/SiO2 composites showed non‐catastrophic behaviour resulting from extensive fibre pull‐out during the failure process.

This paper investigates the armature reaction field and inductance feature of the hybrid excitation synchronous machine (HESM) with magnetic shunting rotor and brushless field excitation . It is shown that introduction of excitation winding has a significant effect on armature reaction of the HESM . Inductance feature is determined by the saturation of both axial and radial flux path which vary with field current and armature current . A 24kW prototype is developed, and the 3D finite element analysis (FEA) results in accordance with measured results validate the inductance variation of the new HESM .