多軸下における一方向繊維強化複合材料の三次元弾塑性微視力学モデル

抄録

A new formulation of three-dimensional stress-strain relationship based on micromechanics is proposed, thus enabling the individual treatment of the mechanical behavior of fibers and matrix in unidirectional fiber-reinforced composites. By specifying the material constants of the carbon fiber and the matrix resin, the proposed model allows analytical prediction of strain components in the elastoplastic region, using the overall stress components of the composite as boundary conditions (and vice versa, from strain to stress components). The analytical results were compared with numerical results obtained using the finite element method, which shows good agreement under the off-axis tensile loading of a lamina, as well as under multiaxial stress states involving tensile loads in the x- and y-directions and a compressive load in the z-direction of a cube. Furthermore, the proposed model was verified to be consistent with Hill’s anisotropic yield criterion. Additionally, after matrix yielding, the ratio of the equivalent stress increment to the equivalent plastic strain increment, i.e., the strain-hardening coefficient, remained constant under tensile loads applied at fiber orientation angles of 5° or more. These results show the effectiveness and applicability of the proposed three-dimensional model for analyzing the mechanical behavior of unidirectional fiber-reinforced composites under multiaxial loading conditions.