Study on the failure mechanism and model of ceramic matrix composite structures

2017-06-01

【Author】 Zhang Hong;

[Instructor] Song Yingdong;

[Basic information about the author] Nanjing University of Aeronautics and Astronautics, Aerospace Propulsion Theory and Engineering, 2009, Ph.D.

【Abstract】 Ceramic matrix composite materials are one of the important candidate materials for future high thrust-to-weight ratio aeroengines. In order to promote the engineering application of ceramic matrix composite materials in aerospace engines, the failure mechanism and failure model of ceramic matrix composite materials must be studied to develop research methods suitable for mechanical behavior and damage analysis of ceramic matrix composite materials. Based on the crack deflection criterion of energy release rate, this paper uses virtual crack closure technology to calculate the energy release rate of matrix cracks in different propagation paths at the interface, and examines the elastic mismatch parameters, matrix crack expansion length, matrix crack relative expansion length and thermal expansion coefficient. etc. on crack deflection. The results show that when factors such as temperature, thermal matching, and interface are not considered, bidirectional matrix crack deflection is more likely to occur than unidirectional matrix crack deflection; the failure mode of matrix crack expansion in ceramic matrix composites at high temperatures is determined by external load and temperature. The cracks can further expand only when the external load is greater than the closing force caused by temperature. Explain the relationship between the macroscopic mechanical behavior of ceramic matrix composites under tensile load and the three basic failure modes of matrix cracking, interface debonding and fiber fracture from the mesoscopic level. Based on the discretization method of the stress-strain curve of ceramic matrix composite materials, a structural discretization method of the failure process of ceramic matrix composite materials is proposed, which discretizes the failure process of orthogonally laminated ceramic matrix composite materials into the failure process of unidirectional fiber reinforced ceramic matrix composite materials. process, the failure process of unidirectional fiber-reinforced ceramic matrix composites is discretely divided into matrix cracks, interface debonding, and fiber fractures dominate the mesoscopic failure mode... More reduction