Fabrication of Foldable Composite Structures Obtained by Selective Curing of Prepregs Made of Long-fibre Reinforcements Impregnated with UV-curable Resin System

Abstract

Foldable composite structures are bellows-like structures that can be stored in a flat state and deployed to a finite volume after folding. These composite structures are being increasingly demanded for numerous engineering applications including aerospace, aeronautics, robotics and medical. In this study, we report an original processing route for obtaining foldable composite laminates. These composite laminates were obtained by selectively curing pre-impregnated materials that were made of three layers of plain weave fabrics impregnated with an UV-curable epoxy-acrylate resin system. After selective curing, the composite laminates were made of rigid domains (cured zones) connected by flexible domains (uncured zones) that played the role of hinges upon folding. The selective curing of the photocurable resin system was performed using two different approaches. The first approach consisted in depositing UV-blocking masks designed numerically onto the surface of pre-impregnated materials before placing them inside the chamber of an UV-curing machine. The second one consisted in using a Digital Light Processing (DLP) 3D printing machine. The UV-curable epoxy acrylate resin exhibited fast curing kinetics characterized by a gelation time on the order of 1 s. Hence, both types of approaches enabled foldable composite laminates with very short time cycles (≈ 5 to 10 s) to be obtained. The as-obtained pre-impregnated sheets were folded into 3D composite structures and then irradiated with UV-light. This original fabrication method is versatile enough to provide a wide diversity of composite part geometries that are promising for many engineering applications. The observations of the microstructure of processed samples revealed that the reinforcement fabrics were rather well impregnated by the epoxy acrylate resin. These observations also tended to show that both types of approaches enabled a complete and efficient in-depth curing of the resin system.