Analysis of the Microstructure and Deformation of Woven Composites Using Microfocus X-ray Diffraction

Unidirectional (UD) prepreg based laminates, consolidated in an autoclave, have been the principal material choice for the composites industry especially for aerospace application. There are concerns, however, about the damage tolerance and compression after impact (CAI) performance of UD composites, in addition to the high manufacturing and material costs. In recent years, the composites industry has been pursuing a cost reduction strategy through various affordable composites initiatives, and at the same time trying to improve damage tolerance. Textile preforms, in the form of interlaced or stitched tow assemblies, are prime candidates for replacing UD prepregs in order to reduce costs and improve damage tolerance. They can be used in both prepreg and dry forms. In the dry form, textiles are easy to handle, have unlimited shelf life and easy to drape over complex surfaces. However, interlaced textiles in the form of woven or braided structures have complex tow geometry leading to complex strain fields around interlacements. Additional complexity arises from the fact that tows deform readily during draping/forming and consolidation processes leading to further changes in local geometry and strain fields.