3D FE-modeling of surface and anisotropy effects during micro-buckling in fiber composites

A 3D finite element model is proposed and a study is carried out of the surface and fiber anisotropy effects during fiber micro-buckling in fiber-reinforced composites. The cases of both transversal isotropic and isotropic fibers with round and rectangular cross-sections are studied. The model accounts for the distinct difference in mechanical properties of the reinforcement and the matrix. Perfect bonding at the fiber-matrix interfaces is assumed. For simplicity, single fibers in a matrix are considered during the calculations. An eigenvalue analysis of the considered systems fibers-matrix subjected to axial compression is performed. Calculations show that the surface effects result in an increase of the buckling wavelength and in a significant decrease of the critical shortening for both isotropic and anisotropic fibers.