Process-microstructure relationships of 2-step and 4-step braided composites

This paper presents a comprehensive study of three dimensional 2-step and 4-step braided composites. The analysis includes the geometric model of unit cells, identification of key process parameters, limiting geometries of yam jamming, and microstructural characteristics (i.e. yam orientation and fiber volume fraction). Since several types of unit cells are identified in the thickness and width directions of 2-step and I-step braided composites, characterization of microstructures is based upon the macro-cell, which occupies the entire cross-section and the unit pitch length of the sample. Finally, processing windows are identified for assessing the effect of various geometric and process parameters on the attainable fiber volume fraction of the composites.