Advanced reinforcement systems for intermetallic applications
A 2-D axisymmetric model was employed to determine the magnitude of the radial, axial, and hoop stresses caused by the thermal expansion difference between fiber and matrix and which result from the fabrication temperature cycle. Finite element analysis was conducted for single fiber model systems based on SCS-6/Ti3Al+Nb and Al2O3/NiAl. The stress distribution due to the imposition of a graded intermediate layer for each system was determined and included variables of layer thickness and gradation in interlayer chemistry in order to vary the expansion gradient between fiber and matrix. Thermal cycling tests were conducted on sputter coated SCS-6 fibers selectively coated with Ti3Al+Nb, with and without an intermediate layer. Cracking of the Ti3Al+Nb layers was prevented by an interlayer based on Ti-TiN-Ti. The interlayer thickness appeared critical to its efficiency. Similarly, for the case of Al2O3/NiAl, an intermediate layer consisting of a Ni bond coat on the sapphire fiber followed by a graded Al2O3-NiAl layer did not crack when given a thermal excursion to 1100 C and then cooled to room temperature. Acoustic emission tests on single fiber specimens were unsuccessful in detecting load drops associated with the successive fracture of the fiber. For the SCS-6/Ti3Al system this was the result of several factors which included the matrix/fiber ratio and poor bonding of the matrix and fiber. In the case of the Al2O3/NiAl system brittle failure of the NiAl matrix precluded fiber breakdown during tensile loading.
- Research Organization:
- Textron Lycoming, Stratford, CT (United States)
- OSTI ID:
- 6462715
- Report Number(s):
- N-93-22875; NASA-CR--4488; E--7557; NAS--1.26:4488; CNN: NAS3-25970; RTOP 510-01-50
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360603* -- Materials-- Properties
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BONDING
CALCULATION METHODS
CHALCOGENIDES
CHEMICAL REACTIONS
CRACKING
DECOMPOSITION
FABRICATION
FIBERS
FINITE ELEMENT METHOD
INTERMETALLIC COMPOUNDS
JOINING
MATERIALS
MATRIX MATERIALS
NICKEL ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
NUMERICAL SOLUTION
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS
REINFORCED MATERIALS
STRESSES
THERMAL CYCLING
THERMAL STRESSES
THERMOCHEMICAL PROCESSES
TITANIUM ALLOYS
TITANIUM BASE ALLOYS