Design tools for circular overbraiding of complex mandrels

Circular braiding is increasingly used to manufacture free-form tubular composites that replace metal primary structural components. A high repeatability and the simultaneous deposition of hundreds of yarns makes braiding suited for automated series production of composite preforms. The inhomogeneous and anisotropic material properties of composites add to the design degrees of freedom, allowing tailoring for specific requirements. This also makes composites more challenging for designers, especially when taking into account the manufacturing constraints of the braiding process.

The objective of this work is to develop braiding design charts for simple braided component designs and to develop fast kinematic braiding process simulation software for more complex designs. In this regard, the following three problems are addressed in an increasing level of detail:

First, circular overbraiding on complex mandrels currently lacks automatic generation of machine control data that provides the braid angle distribution matching the braid's required structural properties. To solve this limitation, an inverse kinematics-based procedure was designed and implemented. This procedure results in a computation time of seconds.

Secondly, removing the correct spools from a machine for a desired braid pattern to braid, for example, a small product on a large machine, can be error-prone. Novel procedures were presented for converting braid patterns to and from spool patterns to avoid trial-and error for finding the correct spool pattern for a given required braid pattern.

Thirdly, an incorrect braid thickness can lead to problems when inserting the braided preform in the mold for downstream resin injection, and it can affect the structural properties and the weight. For this purpose, the braid meso-geometry geometry was parametrized. This approach can be readily integrated in analytical, kinematic, or finite element models.

To avoid simulation for simple designs, novel design charts were proposed for biaxial braids. The charts enable a quick feasibility assessment prior to or instead of braiding process modeling or physical experimentation. For more complex designs, the kinematic models proposed in this work have been implemented in the braiding process simulation software `Braidsim', taking the braiding machine control data as input and generating the composite layup or vice versa.