UWE Bristol Engineering showcase 2015

Oliver Marks
MEng Aerospace Manufacturing Engineering
Project Supervisor
Dr David Richardson
Integrated Composite Rib to Cover Interface Development
Introduction
As the technology behind commercial civil aircraft becomes more advanced
so too does the need to develop the design of the components within them
(Kroo, 1995). Not only with respect to driving down cost but also as the result
of ever tightening regulations on fuel efficiency and environmental impact. As
a result the need to move away from ‘conventional’ configuration aircraft
designs and towards a new optimised lightweight design becomes ever more
paramount.
Wing box covers are comprised of a curved wing skin with a number of ‘T’
shaped stringers (Airbus A350) bolted to it, these stringers are designed to
increase the skin’s ability to withstand buckling loads through an increase in
stiffness. In contrast to the spars in order to increase the deposition rate the
skins are manufactured using UD prepreg through an ATL process (explained
in 4.2.1.2) during which the material is deposited onto a curved tool surface
which controls the outer surface of the wing.
The rib components in the lateral wing box are assembled in the chord-wise
direction and help to keep the aerofoil’s aerodynamic shape during flight
where the aerodynamic loads and pressures are working to deform the wing.
These parts are crucial as they effectively connect the different parts of the
structure together subsequently providing a load path between them. This
load path is shown in figure 10, during service the ribs are subjected to both
tensile and compressive forces due to the torsion and bending present in the
wing structure, these loads are commonly referred to as ‘Brazier Loads’.
Analysis
The product designed within this project is what’s known in industry as a rib
foot, this is the component within the wing box which accommodates the
fixing between the rib and the cover.
Finite Element analysis was carried out on the conceived concepts to establish
a detailed knowledge of how they would perform in service. These designs
were patented as was the corresponding manufacturing process, resulting in
a total of four registered patents.
Thermal analysis of the desired tooling concept was also completed with a
view to using thermal expansion to consolidate the composite from which the
part was manufactured.
Project summary
Development of a novel rib foot concept in
terms of structural performance and
manufacturability.
Project Objectives
• Literature Review on design and
manufacture with composites.
• Blank sheet design of Rib-to-Skin
Attachment component capable of being
manufactured at rate.
• Initial design review/down-selection.
• Initial Finite Element Analysis (FEA) of
down-selected concepts.
• Further down-selection of final concept
based on FEA findings.
• Detailed FE optimisation and sizing of
final concept taking into account weight,
waste, rate and structural performance.
• FE modelling of thermal expansion tooling
concept.
Project Conclusion
The objectives of the project were all met
and a final optimised design was produced
for test. This design outperformed all
competition in terms of performance and
also when considering the ease of
manufacture of the component compared to
conventional designs.