陶瓷基復合材料結構失效機理及模型研究.pdf

1、南京航空航天大學博士學位論文陶瓷基復合材料結構失效機理及模型研究姓名：張鴻申請學位級別：博士專業(yè)：航空宇航推進理論與工程指導教師：宋迎東2009-12陶瓷基復合材料失效機理及模型研究 II Abstract Ceramic matrix composi

2、tes are potential candidate materials for future aero engine of a high thrust to weight ratio.Comprehensive research of failure mechanisms and failure models must be conducted to promote engineering application of cerami

3、c matrix composites，and to develop performance prediction methods and damage research technology of ceramic matrix composites. An energy criterion based the energy release rates is used to study matrix crack deflection a

4、t interface in ceramic matrix composites.The energy release rates of possible crack paths are estimated by applying the virtual crack closure technique, and the effects of elastic mismatch parameters, the crack growth le

5、ngth, the relative crack growth length, and thermal expanding coefficient are analyzed on crack deflection of the matrix. The results show that double matrix crack are more likely to expand than single matrix crack if no

6、t consider the effects of temperature, thermal expansion match and interface performance.Failure models of matrix crack at the interface depends on closing forces caused by load and temperature at high temperature,and ma

7、trix cracks at the interface can be able to expand only the closing force caused by load is greater than that caused by temperature. Analyzed failure mechanism of ceramic matrix composites under uniaxial tensile loading

8、and studied the mechanical relation between common characteristic of the stress-strain response and three dominant damage modes: matrix cracking, interface debonding and fiber breakage through analyzing the damage micros

9、tructure. Based on discrete regions method of stress-strain curve, discrete structure method is set up to divide laminated ceramic matrix composites into unidirectional ceramic matrix composites, and to divide stress-str

10、ain curve of unidirectional ceramic matrix composites into different regions which characterize three dominant damage modes. Unidirectional tension testing methods and testing systems for unidirectional C/SiC composite a

11、re studied. Specimen geometries and gripping fixture are designed, and the tensile test of unidirectional C/SiC is conducted successfully. Elastic modulus, strength and stress-strain curves of test are obtained. In-situ

12、of damage evolution and fracture are researched by analyzing the fracture surfaces of damaged specimens. Assembled unified macro- and micro-mechanic constitutive model with failure criterias and damage evolutions of thre

13、e dominant damage modes, a unified macro- and micro-mechanic constitutive model coupled with damage is improved to predict macro-mechanical properties of unidirectional and Laminates ceramic matrix composites. Keywords: