Thermomechanical Behavior of Functionally Graded Materials
Final rept. 1 May 95-31 Jul 98
TEXAS A AND M UNIV COLLEGE STATION DEPT OF MECHANICAL ENGINEERING
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The research involved developing theoretical formulations and finite element analyses of the thermomechanical, transient response of functionally graded cylinders and plates. Nonlinearities geometric and material, thermomechanical coupling between elastic deformation and heat transfer, and power-law distribution of the two-constitutent material variation through the thickness were accounted for in the formulations. The first-order shear deformation plate theory is used for the kinematics of the plate problem. Numerical results of the deflections, temperature distributions, and stress distributions in the cylinder and plates are calculated. Parametric studies with respect to varying volume fraction of the metal in metal-ceramic plates is conducted. The effect of the temperature field imposed on FGM plates is discussed. It is found that the response of the plate with material properties between that of the ceramic and metal is not intermediate to that of the ceramic and metal plates. The important issue of brittle-ductile mixtures is also addressed in the closing stages of the research, although it requires further study. Yield stresses of the ceramic-metal mixture are obtained using the mixture theory. Yielding within the mixture is assumed to occur when the partial stresses in the metallic component satisfy the classical J2 criterion. Further study of inelasticity and fracture of functionally graded materials must be undertaken. Also, extension of the present work to functionally graded shell structures is recommended.
- Laminates and Composite Materials