UWE Bristol Engineering showcase 2015
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Barry Bartlett<br />
MEng Aerospace Design <strong>Engineering</strong><br />
Design & Analysis of Composite Repair Patches – Part B<br />
Project Supervisor: Ramin Amali<br />
This investigation involves producing a mathematical representation on how the physical orientation of a composite<br />
patch alters Tsai Hill factor of safety of a repaired composite panel under tensile loading. Initially a literature review of<br />
previous studies was conducted. A square composite panel was designed, with a length of 1m. An area of material<br />
was removed from the centre to represent an afflicted area, in need of repair.<br />
Using FEA, the relationship between Stress Concentration<br />
factor and the Fibre Orientation of a single layered notched<br />
composite patch was established. With this data, a means<br />
of theoretically simulating a patch repair method on a<br />
notched composite panel was discovered. By using the<br />
localised stress concentration factors for each layer, the Tsai<br />
Hill Factor of Safety (FOS) of a repaired composite panel<br />
could be determined, before and after a patch is applied. A<br />
relationship between the patch size and the Tsai hill FOS<br />
was then determined using FEA analysis<br />
Stress in Direction 1/Pa<br />
8500000<br />
8000000<br />
7500000<br />
7000000<br />
6500000<br />
6000000<br />
5500000<br />
Stress in Direction 1 vs Patch size<br />
5000000<br />
450 550 650 750 850 950 1050<br />
Length of each side of the Patch/mm<br />
K1<br />
12.00<br />
10.00<br />
8.00<br />
6.00<br />
4.00<br />
2.00<br />
0.00<br />
K1 Between 0 and 180 Degrees Fibre Orientation<br />
0 20 40 60 80 100 120 140 160 180 200<br />
Fibre Orientation/Degrees<br />
A relationship between the patch size and the Tsai<br />
hill FOS was then determined using FEA analysis. It<br />
was shown that the local stress in direction 1 of a<br />
notched panel converged when the patch had a<br />
length of 700mm. This length was chosen for<br />
analysis of patch orientation on Tsai Hill FOS. Using<br />
a notched panel of 4 layers, each with a 45 degree<br />
fibre orientation, FEA analysis was conducted to<br />
determine how patch orientation and fibre<br />
orientation manipulated the Tsai Hill FOS. This was<br />
done for a patch of 2 layers with the same fibre<br />
orientation.<br />
Results show that for this scenario, the<br />
optimum patch orientation is 33<br />
degrees for a patch of two layers, each<br />
with an identic fibre orientation, The<br />
maximum change in Tsai Hill was 0.91%<br />
in these three cases, with an increase<br />
average of 0.55% overall<br />
Tsai Hill FOS<br />
A final study shows that there is a<br />
polynomial relationship between fibre<br />
orientation of a patch and the Tsai hill<br />
of a panel.<br />
Tsai Hill<br />
2.6<br />
2.4<br />
2.2<br />
2<br />
1.8<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
Conclusion<br />
Graphical Illustration of Equation 6 between -50 and 50<br />
Degrees Patch Orientation<br />
1.41<br />
1.405<br />
1.4<br />
1.395<br />
1.39<br />
1.385<br />
-50 -40 -30 -20 -10 0 10 20 30 40 50<br />
Patch Orientation<br />
All 45 Panel, 2 Layer Patches<br />
Tsai Hill vs Fibre Orientation<br />
0 10 20 30 40 50 60 70 80<br />
Fibre Oreintation of Patch