UWE Bristol Engineering showcase 2015

Barry Bartlett
MEng Aerospace Design Engineering
Design & Analysis of Composite Repair Patches – Part B
Project Supervisor: Ramin Amali
This investigation involves producing a mathematical representation on how the physical orientation of a composite
patch alters Tsai Hill factor of safety of a repaired composite panel under tensile loading. Initially a literature review of
previous studies was conducted. A square composite panel was designed, with a length of 1m. An area of material
was removed from the centre to represent an afflicted area, in need of repair.
Using FEA, the relationship between Stress Concentration
factor and the Fibre Orientation of a single layered notched
composite patch was established. With this data, a means
of theoretically simulating a patch repair method on a
notched composite panel was discovered. By using the
localised stress concentration factors for each layer, the Tsai
Hill Factor of Safety (FOS) of a repaired composite panel
could be determined, before and after a patch is applied. A
relationship between the patch size and the Tsai hill FOS
was then determined using FEA analysis
Stress in Direction 1/Pa
8500000
8000000
7500000
7000000
6500000
6000000
5500000
Stress in Direction 1 vs Patch size
5000000
450 550 650 750 850 950 1050
Length of each side of the Patch/mm
K1
12.00
10.00
8.00
6.00
4.00
2.00
0.00
K1 Between 0 and 180 Degrees Fibre Orientation
0 20 40 60 80 100 120 140 160 180 200
Fibre Orientation/Degrees
A relationship between the patch size and the Tsai
hill FOS was then determined using FEA analysis. It
was shown that the local stress in direction 1 of a
notched panel converged when the patch had a
length of 700mm. This length was chosen for
analysis of patch orientation on Tsai Hill FOS. Using
a notched panel of 4 layers, each with a 45 degree
fibre orientation, FEA analysis was conducted to
determine how patch orientation and fibre
orientation manipulated the Tsai Hill FOS. This was
done for a patch of 2 layers with the same fibre
orientation.
Results show that for this scenario, the
optimum patch orientation is 33
degrees for a patch of two layers, each
with an identic fibre orientation, The
maximum change in Tsai Hill was 0.91%
in these three cases, with an increase
average of 0.55% overall
Tsai Hill FOS
A final study shows that there is a
polynomial relationship between fibre
orientation of a patch and the Tsai hill
of a panel.
Tsai Hill
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
Conclusion
Graphical Illustration of Equation 6 between -50 and 50
Degrees Patch Orientation
1.41
1.405
1.4
1.395
1.39
1.385
-50 -40 -30 -20 -10 0 10 20 30 40 50
Patch Orientation
All 45 Panel, 2 Layer Patches
Tsai Hill vs Fibre Orientation
0 10 20 30 40 50 60 70 80
Fibre Oreintation of Patch