A Fracture Mechanics Study of a Strong Interface: The Silicon/Glass Anodic Bond. Ph.D. Thesis
The results are presented of an intensive experimental/computational study of the relationship between the macroscopic fracture behavior of specimens incorporating strong, precracked, brittle bimaterial interfaces and the properties of the interfacial region. The silicon/Pyrex glass anodic bond was chosen because glass and silicon are almost ideally brittle and they form a strong, covalently bonded interface. Compact tension sandwich specimens were fractured by rising load testing, and kink angle and fracture resistance were measured as a function of bonding temperature and mixity of the applied loading. Interface cracks were observed to kink into the more compliant glass over the majority of the applied loading phase angle range. Under remote Mode 1 loading, kink angles into the glass increased from 15 deg to 28 deg as bonding temperature increased from 300 to 450 C. This was an initially surprising result, given that the residual compressive stresses in the glass due to thermal contraction mismatch also increase with bonding temperature. Also observed was a regime of stable crack growth which preceded catastrophic fracture. Fracture resistance was measured both at the initiation of kinking and at the critical load. Values for the former decreased with increasing loading phase angle over the majority of the applied loading range. Values for the latter were limited at the value for bulk Pyrex glass of 0.75 MPa-m(exp 1/2). Correlations between these results and trends in sodium concentration, elastic modulus, and thermal residual stresses were observed. The results could be qualitatively accounted for in terms of expectations based on recent developments in the theory of linear elastic bimaterial fracture mechanics. Computations based on the models of He and Hutchinson for kinking behavior of interface cracks were performed for the mixed mode loading study, using values for interface stress intensity factors obtained from a finite element analysis of the specimens.
- Research Organization:
- Minnesota Univ., Duluth, MN (United States). Natural Resources Research Inst.
- OSTI ID:
- 236771
- Report Number(s):
- N-96-21494; NIPS-96-33319; TRN: 9621494
- Resource Relation:
- Other Information: TH: Ph.D. Thesis; PBD: Jan 1994
- Country of Publication:
- United States
- Language:
- English
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