2022/05/30
3D printing to help shape braided composites
Laboratoire de Structures de Fibres et Composites Avancés (labSFCA, Polytechnique Montréal), Centre Technologique en Aérospatiale (CTA), CTT Group (gCTTg), SphèreCo Technologies Inc. (April 2018 to October 2021)
Objectives
To 3D print prototype tooling for robotic braiding assistance and for resin vacuum infusion moulding, that would use to develop aeronautical parts.
Background
Commercial aircraft are currently made with several composite components. The aircraft’s structural composite parts are made from carbon fibres bonded by a polymer matrix. To produce these parts, the fibres are first assembled with an organized woven reinforcement. This reinforcement is then draped over the tooling before transferring a liquid polymeric resin to impregnate the carbon fibres. Heat treatment is then used to cross-link or solidify the resin. Each stage of this process is validated through the production of parts in an effort to maintain their quality, repeatability and performance while ensuring passenger safety. These validations require tooling that can cause development costs to balloon. The four project partners therefore joined forces to develop a composite aircraft fuselage frame. The objective was to reduce tooling and prototyping costs with 3D printing.
The challenge
The composite fabric, also known as fibrous reinforcement, is made using a braiding machine that interweaves carbon threads to shape a three-dimensional braid. The threads are deposited on a moving mandrel through a braiding machine using a 6-axis robot. But the mandrel’s design creates challenges in terms of its size and mass. The alignment of sections must be perfect and free of surface defects to avoid damaging the deposited carbon fibres. The tooling used to manufacture the vacuum infusion composite also creates challenges. Process temperatures reach 180°C. The tooling’s mechanical strength must be guaranteed under these conditions. Another challenge involves the tooling’s thermal expansion control (αtherm); it can induce deformations in the manufactured part because the polymers’ αtherm is greater than that of metals. Attention is given to any possible dependence between the printing orientation and the tooling’s αtherm. In addition, the polymer tooling interface must be inert to the part’s consumables and materials, here the infusion resin. The final challenge involves the temporal evolution of the tooling’s geometric integrity.