Ultra-tough and in-situ repairable carbon/epoxy composite with EMAA

Abstract

Preforming is a common process in the manufacture of net-shaped composites, and there is a critical need for technologies that improve manufacturing speed without adversely impacting the interlaminar fracture toughness. Furthermore, composite structures that are repairable in-situ have potential for significant cost and performance benefits. This paper presents a new multi-functional composite system that combines ultra-high interlaminar fracture toughness with exceptional repair efficiency and is seamlessly integrated into the braiding process for rapid preform manufacture. The co-braided repair agent, EMAA, is shown to improve the interlaminar fracture toughness by over threefold, while enabling full recovery of the fracture properties via a thermal repair process. The resistance to crack initiation and crack propagation were strongly influenced by the geometric shape and spatial distribution of the EMAA which, in turn, was dictated by the preforming time. A new strategy is developed to produce a 3D fused EMAA network that enables the effective delivery of the repair agent into the delamination cracks and a greater than 100% recovery to the steady-state fracture toughness following delamination repair. The EMAA composites developed in this study exhibited repeated (at least three cycles) in-situ delamination repair abilities.