EFFECT OF COATINGS WITH SMOOTHLY CHANGING TRANSVERSE RIGIDITIES ON THE STIFFNESS OF ENCAPSULATED ANISOTROPIC FIBER COMPOSITES
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THEOCARIS, PS
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DEMAKOS, CB
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The beneficial role of anisotropic coatings with radially dependent transverse stiffness on the improvement of the whole stiffness of the fiber composite is presented in this paper. Such a typical composite is studied as being, macroscopically, a transversely isotropic material by arranging the variation of the effective moduli in its respective representative volume element. This model is formed by a transversely isotropic cylindrical fiber, a transversely isotropic cylindrical annulus as coating of the fiber and an annulus of isotropic matrix covering the encapsulated fiber. The material surrounding the matrix, called the equivalent composite, corresponds to a fictitious material equivalent of the matrix together with the rest of the fibers included in the real composite and therefore attains effective moduli, which average the actual mechanical properties of the composite. Solutions are established in a closed form for the longitudinal and transverse elastic moduli, E(Lc) and E(Tc) of the composite, and for the shear modulus, G(Tc), for various composite models. The study of the variation of these mechanical properties in terms of the percentage amount of the matrix reveals interesting information concerning the overall stiffness of the composite, which is influenced by the extent, as well as by the mechanical properties of the coatings.
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