Experimental and numerical studies of process variabilities in biaxial carbon fiber braids

Abstract This paper investigates the manufacture of biaxial carbon fiber braids and the influence that different machine settings have on variability of the textile architecture produced. In parallel, numerical simulations of the braiding process with these different machine settings have been conducted. For these studies yarn tension and process speed are varied to generate cylindrical biaxial braids with an average braid angle of±45°. The overall preform quality is characterized by means of variability in braid angle, yarn width, cover factor and fiber damage, using a variety of experimental techniques. Furthermore, from the final infused composite variations in yarn cross-section dimensions have been measured. A method is presented to transfer braid process simulation results to a detailed three dimensional finite element model of the architecture using a technique based on thermal expansion and compaction simulation. This method also allows the possibility to introduce experimentally observed variability in yarn cross-section dimensions. Such a model provides a valuable starting point for mesoscopic infusion or mechanical analysis of the textile composite. A comparison between experimental and numerical results shows that the process simulation can well reproduce the real braid angles in terms of mean value and scatter under different machine configurations and that the meso-scale textile model gives a good reproduction of the true textile architecture.