Characterization of the dissipative large deformation bending response of dry fabric composites as occurs during forming

Abstract

Bending rigidity is known to play a significant role in the formability of composite fabrics, as it can affect wrinkles formation and reduce the mechanical properties of the final part. However, measuring the highly nonlinear dissipative bending behaviour of unconsolidated fabrics undergoing large deformation, is an ongoing challenge. In this article, a customized setup is employed to capture the bending as well as reverse bending responses of unconsolidated fabrics under large deformation (up to ±90o bent angle). As a test case, a typical fiberglass fabric that is thick and has high areal density, as well as a carbon fiber fabric with lesser thickness and lower areal density are considered and compared. In addition, the response of the fabrics was compared to that of individual yarns, suggesting that the interlaced architecture and the dissipative behavior of yarns affect the effective bending rigidity, along with the ensuing hysteresis effects during loading/unloading. Furthermore, when the unconsolidated fabrics were oriented off-axis relative to the bending axis, the bending rigidity interacted with the in-plane trellising (reach to maximum of 3.3o shear at full bent angle), suggesting that the classical laminate theory would not apply to capture shear-bending coupling in dry fabrics.