Residual Stresses in Fibrous Metal Matrix Composites: A Thermoviscoplastic Analysis
The vanishing fiber diameter model together with the thermoviscoplasticity theory based on overstress are used to analyze the thermomechanical rate (time)-dependent behavior of unidirectional fibrous metal—matrix composites. For the present analysis the fibers are assumed to be transversely isotropic thermoelastic and the matrix constitutive equation is isotropic thermoviscoplastic. All material functions and constants can depend on current temperature. Yield surfaces and loading/unloading conditions are not used in the theory in which the inelastic strain rate is solely a function of the overstress, the difference between stress and the equilibrium stress, a state variable of the theory. Assumed but realistic material elastic and viscoplastic properties as a function of temperature which are close to Gr/Al and B/Al composites permit the computation of residual stresses arising during cool down from the fabrication. These residual stresses influence the subsequent mechanical behavior in fiber and transverse directions. Due to the viscoplasticity of the matrix time-dependent effects such as creep and change of residual stresses with time are depicted. For Gr/Al residual stresses are affecting the free thermal expansion behavior of the composite under temperature cycling. The computational results agree qualitatively with scarce experimental results.
KeywordsResidual Stress Fiber Direction Transverse Strain Rensselaer Polytechnic Institute Residual Stress State
Unable to display preview. Download preview PDF.
- Dvorak, G. J. and Rao, M. S. M., 1976, “Thermal Stresses in Heat-Treated Fibrous Composites,” ASME Journal of Applied Mechanics, pp. 619–624.Google Scholar
- Hillig, W. B., 1985, “Prospects for Ultra-High-Temperature Ceramic Composites,” Report No. 85CRD152, General Electric Research and Development Center.Google Scholar
- Kreider, K. G. and Prewo, K. M., 1974, “Boron—Reinforced Aluminum,” Composite Materials, Vol. 4, Metallic Matrix Composites, Edited by Kenneth G. Kreider, Academic Press.Google Scholar
- Lee, K. D. and Krempl, E., 1990, “An Orthotropic Theory of Viscoplasticity Based on Overstress for Thermomechanical Deformations,” to appear in International Journal of Solids and Structures.Google Scholar
- Lee, K. D. and Krempl, E., 1990a, “Uniaxial thermomechanical loading. Numerical experiments using the thermal viscoplasticity theory based on overstress,” MML Report 90–1, Rensselaer Polytechnic Institute, March.Google Scholar
- Min, B. K. and Crossman, F. W., 1982, “History—Dependent Thermo—mechanical Properties of Graphite/Aluminum Unidirectional Composites,” Composite Materials: Testing and Design (Sixth Conference), ASTM STP 787, I. M. Daniel, Ed, American Society for Testing and Materials, pp. 371–392.CrossRefGoogle Scholar
- Tompkins, S. S. and Dries, G. A., 1988, “Thermal Expansion Measurement of Metal Matrix Composites,” SPIOBA ASTM STP 964, P. R. DiGiovanni and N. R. Adsit, Editors, American Society for Testing and Materials, Philadelphia, pp. 248–258.Google Scholar
- Tsirlin, A. M., 1985, “Boron Filaments,” Handbook of Composites, Volume 1, “Strong Fibers,” Editors: Watt, W. and Perov, B. V., North—Holland.Google Scholar
- Yeh, N. M. and Krempl, E., 1990, “Thermoviscoplastic Analysis of Fibrous Metal-Matrix Composites,” MML Report 90–2, Rensselaer Polytechnic Institute, March.Google Scholar