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 mod el of unit cells, identification of key process parameters, limiting g eometries of yam jamming, and microstructural characteristics (i.e. ya m orientation and fiber volume fraction). Since several types of unit cells are identified in the thickness and width directions of 2-step a nd I-step braided composites, characterization of microstructures is b ased upon the macro-cell, which occupies the entire cross-section and the unit pitch length of the sample. Finally, processing windows are i dentified for assessing the effect of various geometric and process pa rameters on the attainable fiber volume fraction of the composites.