Predicting the in-plane elastic constants of diamond braided composites

An analytical model based upon repeat unit cell approach is proposed to pre dict the in-plane elastic constants of two dimensional diamond braided comp osites. A new geometrical model is developed which considers the yam undula tion and inter-yam gap in a diamond braided fabric reinforced composite. Th e actual state of yarns in composites is modeled by the use of sinusoidal s hape functions, which employ parameters such as braid construction, yarn ge ometry, inter-yam gap and overall volume fraction to quantify the geometry of braided fabric. Stiffness is predicted by calculating the engineering co nstants for each subcell followed by averaging it over the repeat unit cell 's volume using a combination of iso-stress and iso-strain conditions. Comp osites using four different fabric architectures are fabricated and tested in tensile mode to verify the model. The experimental results indicate reas onable correlation with predicted results. Parametric study is conducted ov er a range of structurally possible geometrical parameters to study the eff ects of braiding angle, yarn aspect ratio and gap on the in-plane elastic p roperties of the textile composite.