Composite forming post-manufacture: reducing complexity and de-risking manufacture

Abstract. Forming is a high-risk operation as the deformation of precursors, such as preforms or prepregs, is difficult to control. Aiming at de-risking manufacturing and improving processing logistics, a new forming concept is presented involving pre-structuring, i.e. producing fully cured flat structure with integrated formable hinge regions, and assembly, where the part is given the targeted shape using localised forming in the hinge regions. Such a technique becomes feasible if (a) the hinges are produced with the aid of covalent adaptive networks (CANs, cross-linked polymers that can flow when heated above a certain temperature), (b) the excess fibre length (that can occur in the process of forming) is incorporated at the pre-structuring stage. Hence, we pursue an idea of multi-matrix continuously-reinforced composites (MMCRC) with embedded fibre path features, where the main body of composites structure is produced with a conventional epoxy matrix and the hinged areas are produced with reformable CANs. The current paper explores the potential and limitations of this technology in manufacturing trials. It is demonstrated that the presented concept can yield high quality solutions. It is highlighted that an improved manufacturing procedure using specially designed and portable machinery would enable application of the MMCRC technology in the field, facilitating repair and efficient transportation.