UWE Bristol Engineering showcase 2015

Michael Symons
MEng - Aerospace Engineering Design
Project Supervisor
Rui Cardoso
THE VALIDATION AND OPTIMISATION OF A WINGBOX USING FINITE
ELEMENT ANALYSIS PART B
Background
The modern engineer can now computationally model the product and analyze and optimize it, simulating the test procedure. However, before the proceedings of this the
computational model must first be validated with the test. Finite element analysis (FEA) is an example of technology advancement and has become a common usage in
design development.
This type of analysis is particularly used for aircraft wing design such a wing-box which is made of structural elements (spar, skin and stringer). Design engineers use FEA to
simulate the wing-box and optimize the most suitable use of these elements.
One behavior engineers evaluate in wings is buckling. Buckling is a failure caused by a compressive load that exceeds the materials compressive stress abilities. This
commonly occurs in the wing spar and skin.
Composites are also analyzed and optimized. To formulate the material properties and computationally evaluate the composite behavior to suitably consist of the most
efficient layup and thickness; there are evaluation techniques available that are largely used in industry; one being Tsai-Hill failure criterion that formulates the factor of
safety of each ply in the composite, given its lamina properties.
Initial Designs
The design used for
analysis was a wing-box
with 2 C-section spars.
One made form Carbon
Fiber and the other from
Fiber Glass
ABAQUS Model
The initial designs were simulated using
FEA software ABAQUS
Experiment
A four point bend was
tested on the models
and validated using
ABAQUS simulations
Spar Buckling and
Roller load vs Wingbox
stiffness
Project summary
This report details the investigation and
development of a preliminary design that was
analyzed experimentally and subsequently
validated using finite element analysis in a
straightforward and user-friendly manner. In
addition to being optimized to perform
effectively in regards to its initial buckling
performance previously evaluated.
Project Objectives
The aim of the project was to simulate and validate an
experimental outcome of a wing design performance
under controlled conditions using finite element analysis.
The design was then optimized to improve the buckling
performance of the design using Tsai Hill Criterion and
wing structural elements.
Validation of the Carbon Fiber Wing-box
The glass Fiber and Carbon Fiber models were validated to a good degree
of accuracy [shown below the glass fiber which has a mean disparity of
3.8%]
Roller Contact Force (N)
160
140
120
100
80
60
40
20
0
-20
Comparison of FEA and Experiment Data on Wing-box
displacement under a uniform load
0 2 4 6 8 10 12
Displacement (mm)
FEA
Experiment
Optimization
The Carbon Fiber wing box was then brought forward for Design optimization.
Applying Stringers and ribs to the design the following conclusions were found:
• the stringer is more affective on the parts where the main stress involved is
compressive. At the top skin where it buckles mainly from load in the y-
direction, the stringer is not as effective.
• Concluding the optimization to reduce buckling; max buckling occurs at the
skin end and where the load is applied. It’s more suitable to apply a rib at
these locations. If the location of load concentration is known, reinforcing
that point is the most efficient and effective option.
Tsai Hill:
FF. OO. SS. =
TT xx
σσ 2 xxxx − σσ xxxx σσ yyyy + TT xx 2 2
σσ yyyy
2
TT yy
+ TT xx 2 2
ττ xxxx
2
SS XXXX
Tsai Hill Criterion was used and modelled in MATLAB to optimize the most
suitable layup to use, sticking with an applied load but the variable being the
layup proportion.
Project Conclusion
Overall, it was concluded that a design under
a complex experimental procedure, simulated
in FEA can be validated to a good degree of
accuracy, respectively; to later be optimized
to improve its buckling performance. The
ABAQUS simulations successfully simulated
spar buckling for the Carbon Fiber model. The
disparity mean ranged from 5% to 9%. The
accuracy for load required to displace the
roller for the Carbon fiber wing-box had an ok
agreement (mean disparity no greater than
35%). The ABAQUS models were able to
simulate the buckling behavior affectively and
a Tsai Hill code was produced in MATLAB to
successfully formulate and optimize the
layup.