AUTHOR=Jimenez Martin Claudia , Maes Vincent K. , McMahon Turlough , Kratz James TITLE=The Role of Bias Extension Testing to Guide Forming of Non-Crimp Fabrics JOURNAL=Frontiers in Materials VOLUME=9 YEAR=2022 URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2022.825830 DOI=10.3389/fmats.2022.825830 ISSN=2296-8016 ABSTRACT=

The increased production rate targets of the aerospace industry has driven the development of dry fibre processes and biaxial Non-Crimp Fabrics (NCFs). Understanding the forming behaviour of NCFs at scale is key to achieving high quality parts at high rates. The bias extension test is commonly used to characterise the shear behaviour of dry fabrics, for example as input to drape forming models. In industry, it is still often used as a standalone material selection tool as part of initial material selection processes. It is however well known that the boundary conditions of this test are often not representative of full-scale forming trials. A direct comparison with wrinkles observed during a forming experiment is carried out to show that the bias extension test overpredicts wrinkle height. Overall, the bias extension is considered unsuitable on its own for predicting preform quality in an NCF forming process where excess length is generated due to part geometry. If the bias extension is to be used as an NCF material ranking tool, wrinkle height data should be captured alongside force shear data, as shown in this study.