Braided preforms are used in many applications to make modern textile composites. Mechanical properties of braided composites are strongly dependent on braided preform’s characteristics such as braid angle and yarn spacing. In this paper, theoretical relationships are presented to predict these parameters in braiding of a mandrel with flat faces. These relationships are very simple in deriving and coding and also they are suitable for sharp edges. It was observed that considering the distance between the yarn’s fell point on the mandrel and guide ring plane is an important issue to calculate an accurate braid angle. Braid angle and yarn spacing was also measured experimentally. Theoretical relations predictions are in close agreement with experimental measurements. The effects of the mandrel aspect ratio and the mandrel eccentricity to produce a part with variable braid angle are investigated. It is observed that while mandrel dimension aspect ratio has no significant effect, the braid angle can be considerably varied from one face to another face by locating the mandrel out of the center of the machine. An optimization process is proposed to find the best mandrel eccentricity to manufacture a preform with desired braid angles on individual faces.

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