Abstract:
Composite materials have been extensively adopted by modern aircraft design
and manufacture. This manufacturing process needs a forming mould. Invar
alloy has been widely used to manufacture moulds for the fabrication of
aeronautics and astronautics composite structures because of its unique low
thermal expansion coefficient. However, Invar is very expensive and the
machining and repair process is difficult and costly. Therefore, to find an
alternative approach to manufacture and repair the Invar mould is would help to
save costs.
Additive Manufacturing (AM) technology is an innovative technology which can
manufacture components layer upon layer directly from a CAD file without the
need of tooling. Unlike conventional machining technologies which remove
materials from a solid block of metal, AM is an additive process which can
significantly save materials. Dissimilar material components can be fabricated
by Wire and Arc Additive Manufacturing (WAAM) process with good
metallurgical joints.
A new, functional tooling approach combining Invar and steel using Wire and
Arc Additive Manufacturing (WAAM) technology is introduced in this research.
Invar is used to fabricate the top part of the tool as it has a uniquely low thermal
expansion coefficient property while the base part of the tool is made of mild
steel to supply strength and save costs.
The research showed that Invar can be successfully deposited on steel using
the WAAM process with high integrity joint. In addition, an FEM model was built
to simulate the deformation of multi-material moulds in the autoclave heating
process. Following on from the results from the FEA-based mould’s deformation
prediction, a parameter compensation method was proposed for the bi-material
mould design and optimisation. The FEM model was verified through a case
study around a composite door from a commercial aeroplane. The results
indicate that the mould deformation can be effectively controlled by parameter compensation and the optimised mould will satisfy industrial tolerance
requirements.
