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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

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