ANALYSIS OF ELASTIC MODULI OF UNIDIRECTIONAL CFRP

Abstract

Elastic moduli of unidirectional and continuous carbon fiber reinforced plastics (CFRP) were analyzed theoretically, taking into account the anisotropic elastic property of the carbon fiber. This analysis is based upon the Eshelby's equivalent inclusion method¹²⁾ and a kind of smearing-out method proposed by the authors.¹⁷⁾ The solution procedure was formulated and specified, so that it could be easily applied to the stress analysis of the CFRP laminates. The procedure was applied to the investigation of the effective elastic moduli of unidirectional CFRP. And it was shown that the longitudinal Young's modulus E^L_c and Poisson's ratio v^TL_c (v^TL_c is the Poisson's ratio when tensile stress is applied in the longitudinal direction only) were almost proportional to the volume fraction of fibers (v_f), and the simple rule of mixture with respect to E^L_c and v^TL_c is available. The shear modulus G^TL_c depends only on G^TL_f, provided that the shear modulus of the matrix G_m=E_m/2(1+v_m) and v_f are constant. However G^TL_c is affected more seriously by the variation of E_m than that of G^TL_f Transverse Young's modulus E^T_c increases considerably with the increase of E^T_f and decreases slightly with the increase of v^TT_f v^TT_c increases with the increase of v^TT_f and increases slightly with the increase of E^T_f. The suffix c, f, m (of the symbols E, v. G) denote composite, fiber and matrix, respectively. Numerical results were also compared with the experimental data reported by Ishikawa et al.¹¹⁾ and the anisotropic elastic modulus of the carbon fiber TORAYCA T300 was estimated.