3D mesomechanical analysis of three-axial braided composite materials

A new analytical mesomechanical approach valid for three-axial as well as 3D braided composite materials is described in this paper. This approach is based on a unit cell scheme and takes into account the geometry and the mechanical properties of both phases, the fiber and the matrix. A finite element analysis has been carried out in order to obtain comparable results between this numerical technique and the new analytical approach proposed in this paper. Two different configurations of 3D braided carbon fiber/epoxy matrix composites have been studied, according to the geometry of the braided preforms: [0 degrees/+/- 20 degrees] and [0 degrees/+/- 30 degrees]. A failure criterion taking into account yarn and matrix degradation has been applied to predict theoretically failure in both configurations. In order to assess the accuracy of the results from both analytical and finite element approaches, an experimental program was performed. A uniaxial tensile stress testing was carried out in both longitudinal and transverse directions of three axial braided specimens. Results obtained in the tests as well as the analytical and finite element approaches will be discussed. (c) 2006 Elsevier Ltd. All rights reserved.