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Effects of thermal cycling on thermal expansion and mechanical properties of sic fiber-reinforced reaction-bonded si3n4 composites
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Bhatt, R. T. Palczer, A. R. |
| Copyright Year | 1994 |
| Description | Thermal expansion curves for SiC fiber-reinforced reaction-bonded Si3N4 matrix composites (SiC/RBSN) and unreinforced RBSN were measured from 25 to 1400 C in nitrogen and in oxygen. The effects of fiber/matrix bonding and cycling on the thermal expansion curves and room-temperature tensile properties of unidirectional composites were determined. The measured thermal expansion curves were compared with those predicted from composite theory. Predicted thermal expansion curves parallel to the fiber direction for both bonding cases were similar to that of the weakly bonded composites, but those normal to the fiber direction for both bonding cases resulted in no net dimensional changes at room temperature, and no loss in tensile properties from the as-fabricated condition. In contrast, thermal cycling in oxygen for both composites caused volume expansion primarily due to internal oxidation of RBSN. Cyclic oxidation affected the mechanical properties of the weakly bonded SiC/RBSN composites the most, resulting in loss of strain capability beyond matrix fracture and catastrophic, brittle fracture. Increased bonding between the SiC fiber and RBSN matrix due to oxidation of the carbon-rich fiber surface coating and an altered residual stress pattern in the composite due to internal oxidation of the matrix are the main reasons for the poor mechanical performance of these composites. |
| File Size | 14573731 |
| Page Count | 21 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19950007884 |
| Archival Resource Key | ark:/13960/t6tx8829s |
| Language | English |
| Publisher Date | 1994-10-01 |
| Access Restriction | Open |
| Subject Keyword | Composite Materials Ceramic Matrix Composites Silicon Carbides Fiber Composites Thermal Cycling Tests Stress-strain Diagrams Thermal Expansion Refractory Materials Fiber-matrix Interfaces Silicon Nitrides Oxidation Fiber Orientation Fracturing Tensile Properties Residual Stress Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
