Effect of various parameters on effective engineering properties of 2 x 2 braided composites

Textile composites can be tailored to meet specific thermomechanical requirements for structural applications. Textile composites have good stiffness and strength properties; moreover, they have potentially better impact and fatigue resistance than laminated composites. Along with good properties, they have reduced manufacturing cost because much of the fabrication can be automated. To exploit these benefits, thorough understanding of the effect of various factors on their material behavior is necessary. Dominant forms of textiles are weaves, braids, and knits. The focus of this research is on 2 x 2 biaxial braided composites, which are considered a potential material for lightweight aircraft and have a wide variety of applications in the recreational, medical, and aerospace industries. Obtaining effective mechanical properties is the first order of concern in any structural analysis. This work presents an investigation of the effect of various parameters such as braid angle, waviness ratio, material properties, and cross-sectional shape on the effective engineering properties of the 2 x 2 braids. To achieve this goal, three-dimensional finite element micromechanics models were developed. Extensive parametric studies were conducted for two material systems: ( 1) glass fiber/epoxy matrix (S2/SC-15) and ( 2) carbon fiber/epoxy matrix (AS4/411-350). Equivalent laminated materials with angle plies and a resin layer were also analyzed to compare the difference in predictions from full three-dimensional finite element analyses of the 2 x 2 braided composites. The predictions are also compared with experimental results for a carbon/epoxy material system.