Comparison of Interlocked Fabric and Laminated Fabric Kevlar 49/Epoxy Composites

Abstract

The mechanical properties of a multilayered, interlocked Kevlar 49 fabric reinforced epoxy composite with roughly a 4% fiber volume fraction in the through-the-thickness direction are reported. These results are compared to those of a standard Kevlar fabric laminate containing the same overall fiber volume fraction. Through-the-thickness reinforcement increases the apparent short beam shear strength by 25%. Actually, the shear failure mode is suppressed by the through-the-thickness reinforcement, and failure is due to yarn kinking on the compressive side of the beam. In contrast, the in-plane properties of the interlocked fabric reinforced composite are lower than those of the standard fabric laminate. For example, the initial tensile modulus is reduced by 35% while the ultimate tensile strength is reduced by roughly 25%. This loss in properties is thought to be due to both the relatively greater crimp in the interlocked fabric used in this study and fiber stress concentrations introduced by the binder yarns.