Analysis of stress concentrations in 2 x 2 braided composites

The stress distribution in braided composites is complex even for simple uniaxial loading. The interlacing of the tows creates a complex load path that results in full three-dimensional (3D) stress distribution. The location and magnitude of peak stresses depend on the particular stress component and vary with various braid architecture parameters such as braid angle and degree of waviness. Finite element analyzes for different braids were performed and it was seen that the peak stresses in the tow mainly occur at the undulating region and along the edges of the tow. Stress distribution in braids was compared with those in equivalent laminates. A considerable volume of the tow (10-45% for the considered range of parameters) had stresses larger than an equivalent lamina. The severity of stresses in a braid as compared to those in an equivalent lamina depends upon braid geometric parameters. Braid angle changes the stress distribution in the tow considerably. However, most of that effect is due to the orientation of the tows in the + and directions and can be eliminated by matching the loading on the tow of different braids. The severity of peak stresses seems to be increasing linearly with an increase in waviness ratio.

Analysis of stress concentrations in 2 x 2 braided composites Academic Article