Enhancement of interlaminar fracture toughness in textile-reinforced epoxy composites with polyamide 6/graphene oxide interlaminar toughening tackifier

Although widely used in aviation and aerospace engineering over the last several decades, textile-reinforced epoxy composites always suffer from their relatively poor out-of-plane properties, due to the inherent brittleness of epoxy matrix. In this work, a concept of interlaminar toughening tackifier is proposed to simultaneously enhance the interlaminar properties and process efficiency during manufacture of textile-reinforced epoxy composites via liquid composites molding (LCM) processes. A new interlaminar toughening tackifier polyamide 6/graphene oxide (PA6/GO-1.0) was prepared successfully via in situ polymerization and ethanolic solution precipitation methods. Through sufficient evaluation by standard double cantilever beam (DCB) tests and end notched flexure (ENF) tests, interlaminar fracture toughness of textile-reinforced epoxy composites exhibited an effective enhancement of 80.6% and 36.2% under mode I and mode II deformation, respectively. The mechanism for the excellent interlaminar properties are discussed thoroughly based on careful fractographic study of the delaminated composites. T-peel tests were also performed to assess the interply adhesion properties of PA6/GO-1.0. Moreover, for the best interlaminar fracture toughness, the dosage of GO is no more than 0.05 wt% to the textile reinforcements, providing an economically feasible method to balance the mechanical properties and process efficiency.