A Study of Residual Stresses in Titanium Metal Matrix Composites. Ph.D. Thesis
Residual stress analysis of as-processed SCS-6/Ti-24Al-llNb (at.%) (0)(sub s) metal matrix composite (MMC) was performed using the x-ray diffraction (Sin(exp 2)(sub Psi)) technique. Residual stresses were measured in the alpha(sub 2) a phase of the matrix in orientations parallel, transverse, and 45 deg. to the fiber direction. Stress profiles were determined by successive removal of the matrix from the composite surface by electropolishing. Within 10 to 30 microns of the first fiber plane, the stress levels were found to be lower than those far from the fiber plane. Residual stress measurements performed on the matrix material between the first two fiber rows (second-ply) revealed lower stress levels than those in the outermost matrix layers. The presence of stress gradients normal to the surface of the composite was also revealed in the second-ply region. Residual stresses were also measured after thermal cycling from 150 deg.C to deg. C in an inert atmosphere. Residual stress profiles were also determined in SCS-6/Beta-21S composites in unidirectional (0)(sub 4), cross-ply (0/90)(sub s), and quasi-isotropic (0/+/- 45/90), lay-ups in directions parallel and perpendicular to the fiber direction on the surface ply. For the unidirectional MMC the longitudinal stresses were almost twice the transverse stresses. The stress profile showed a slight increasing gradient towards the fiber-matrix interface in both the longitudinal and transverse directions. On the surface the stresses measured 235 MPa and 130 MPa in the longitudinal and transverse directions respectively, and at a distance of 25 microns from the fiber-matrix interface, the stresses measured 250 MPa and 150 MPa in the same directions. In the cross-ply MMC the longitudinal and transverse stresses were similar in magnitude and measured 200 MPa at the surface and 220 MPa at distance of 25 microns from the fiber-matrix interface.
- Research Organization:
- Cincinnati Univ., OH (United States)
- OSTI ID:
- 237325
- Report Number(s):
- N--96-23219; NIPS--96-34397
- Country of Publication:
- United States
- Language:
- English
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