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Aluminium and its alloys used in aircraft
Suggested answers
Activity 1
Discuss why there has been a change from one material to another in aircraft development?
Table 1. Potential structural aircraft materials
Figure 1. Structural materials mass distribution on the Boeing 747 and 777
Source: Robinson, J.S., Elements
magazine. University of Limerick Publication, Issue 2, pp.19-20, September 1994).
The first materials that were used were the ones readily available at that time. Spruce and bamboo are strong yet lightweight; bamboo is hollow which helps to cut down on weight. Then, steels were used as they had better strength for larger aircraft but they were heavy so there was need for a better solution. Aluminium proved to be easily strengthened by heat treatment processes such as precipitation hardening. Nowadays lithium alloys are used which is very light but stiff and strong. Newer materials still, such as carbon fibre and Kevlar are paving the way further forward in aircraft design. They are extremely stiff and ultra lightweight. All this has meant that aircraft are now more fuel efficient, can carry heavier payloads, and can fly farther and faster than ever before.
Activity 2
List the three main reasons why aluminium alloys are used instead of pure aluminium?
- Increased strength to weight ratio over pure aluminium.
- Increased stress corrosion cracking and fatigue resistance.
- Improved stiffness and resistance to bending.
Activity 3
Describe how an age hardening rivet could be inserted into the wing of an aeroplane during assembly?
The rivet would be made from an appropriate aluminium-copper alloy. The rivet would be kept refrigerated, to slow down the age hardening effect. Once a correct size hole has been drilled through the skin and the frame of the wing, the rivet would be set in place using a suitable riveting gun. It would easily go in “soft” and once left there, over time, it would harden and therefore increase in strength, thus holding the two parts firmly together.
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