Deformation characteristics and formability of a tricot-stitched carbon fiber unidirectional non-crimp fabric

Abstract Deformation characteristics and formability of a heavy-tow unidirectional non-crimp fabric (UD-NCF) was studied. The fabric response under in-plane shear and biaxial tension loading (experienced during forming operations) was first investigated. Local deformations captured by measuring tensile/compressive strains in the stitching segments traversing the carbon fiber tows was correlated to the fabric three-stage macroscopic response during shear tests. Biaxial tension tests were performed at room and elevated temperatures with different displacement ratios to mimic typical preforming processes. Variations in biaxial displacement ratio revealed the interdependency of the fabric orthogonal tensile deformation modes, while temperature did not influence the response. Next, single layer hemispherical and flat punch draping experiments were performed to monitor defects (wrinkling) and capture strain contours, which correlated with in-plane shear and biaxial tension deformations. The results yield an improved understanding of the complex multiscale deformation modes for the heavy-tow UD-NCF and represent important data sets for constitutive models.