Mechanics of cracking for composite material
Cracking in the system is responsible for the reduction of strength for the vast majority of engineering materials. The object of this thesis is to introduce the Linear Elastic Fracture Mechanics to discuss the state of knowledge on the cracking behavior of Composite Materials. This has implications for the science of the subject - basic understanding and modeling - and for practical considerations to aid high performance engine development. Several models were proposed in this study. Tunneling, a commonly observed cracking process, is inspected in this thesis: a new model for tunneling crack is introduced. Formula for steady-state energy release rate G[sub ss], which make it convenient for finite element analyses, is presented, and the relevance of G[sub ss] is studied. The concept is applied to micro cracking in brittle matrix composites caused by thermal expansion mismatch and tunneling cracks in a laminated 0/90 ceramic/matrix composite. Comparisons between experiment results and modeling are also included. Another more practical concern is trying to reconcile design practices for ductile alloys and monolithic ceramics, and thereby provide a theoretical link between design with and of ceramic-matrix composites. For a monolithic panel, even a small hole reduces the load-carrying capacity by a factor of 3: this is notch-sensitive. For a ductile alloy a small hole does not reduce much the load-carrying capacity: this is notch-insensitive. The main goal of that study is to determine the maximum load-carrying capacity of a ceramic-matrix composite panel with a hole. The basic model is large-scale bridging. An extended model, two-level-bridging model, is also included. Most engineering composite components exhibit failure behaviors that are governed by anisotropic and heterogeneous characteristics. In this thesis, a spatial rescaling was found to reduce plane elasticity problems for orthotropic materials.
- Research Organization:
- California Univ., Santa Barbara, CA (United States)
- OSTI ID:
- 7070911
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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