UWE Bristol Engineering showcase 2015

Jonathan A Everard
MEng Aerospace Design Engineering
Project supervisor
Dr Rui Cardoso
Analysis and optimisation of cut-outs in a fuselage
Introduction
In aerospace design, it is critical that weight is saved throughout the aircraft wherever possible, whilst
maintaining strength.
Weight can be saved throughout an aircraft through minimising stress concentrations, as these weaken
components and require reinforcement.
It is therefore beneficial to analyse these stress concentrations, and to be able to optimise the design of
components to reduce their impact on the overall weight of the component.
This investigation in particular sets out to investigate the different methods of analysing the stress concentrations
that occur in a fuselage with cut-outs, and to optimise the design of such cut-outs in order
to reduce the weight of the fuselage as much as possible. Cut-outs in a fuselage are essential. Cut-outs
include things such as doors, to windows, to access panels for internal components and workings of an
aircraft.
Project outline
Two stages of this investigation were completed. The first: to analyse the effect of cut-out shapes on
the stresses in the local section. The optimal shape was determined and carried through to further sections
of the investigation. Reinforcement methods for reducing the stress concentrations in the area
were also tested. Graphs were produced in order to determine the best reinforcement in terms of
strength to weight ratio. The best reinforcement was then optimised to save as much weight as possible.
The second stage largely draws on the conclusions of the first. For the second stage analysis was conducted
on a fuselage section that included a central wing box. The geometry of this wing box affects the
stresses around the cut outs in the local vicinity. The geometry was therefore optimised in order to reduce
the maximum stress in the section. The results and conclusions from stage one were then implemented
here, and the effects of the reinforcements in particular analysed.
The contour plots shown depict the stresses around the cut-outs themselves, and the newly reinforced
fuselage geometry section.
Project Summary
The project set out to investigate and optimise the
effect of the geometry design of a fuselage on the
shear stresses around cut-outs.
Project objectives
The main stage one goal will be to analyse the
stress concentrations around cut-outs for a fuselage
under typical loads experienced over a standard
flight envelope. Flat plates with equivalent
loads and geometries will be tested in FEA software
Abaqus CAE and compared to theoretical
hand calculations.
The main goal for stage two year one is as follows:
Analysis will be conducted on a fuselage section
that includes the forces present from the centre
wing box. This central, crucial geometry will be
modelled and its effect on the stresses and stress
concentrations around cut-outs analysed.
Project conclusion
The accuracy of the FE results greatly depends on
the quality of the mesh. The reinforcement techniques
outlined in stage one prove that adding material
strategically to the area of stress concentration
can drastically improve the performance of
the component overall. This practice usually increases
the component’s strength to weight ratio.
This is a desirable trait in the aerospace industry.
Stage two of this investigation proves that it is possible
to reduce both the mises stress and the shear
stress in the fuselage section, particularly around
the cut-outs.