GLARE Fuselage

Question 1

List the main functions of the GLARE fuselage.

Answer 1

• It is the principal structure of an aircraft. The panels are made of GLARE.
• Requires fatigue resistance, high impact resistance and damage tolerance characteristics. Any significant failure could be catastrophic.
• Needs to be lightweight, capable of withstanding cyclic pressure stresses and improve passenger safety and comfort through thermal and acoustic insulation.
• Must be corrosion resistant, durable against temperature/flames and humidity.

Question 2

What material is best suited for this application?

Answer 2

Glass Laminated Aluminium Reinforced Epoxy. A laminated of glass fibre reinforced plastic and aluminium layers.

Question 3

List some properties of GLARE that make it better suited than other materials.

Answer 3

This has better damage tolerance compared to other composites as delamination occurs less often. It is also more visible due to dents that result from significant impact. The better damage resistance means panels can be made thinner, thus reducing weight.

Better protection from lightning strikes due to conductive material already embedded in the structure.

Question 4

Why is Aluminium not used for this application?

Answer 4

Using Aluminium means that many more manufacturing techniques can be used, unlike GLARE which is very restricted.

Aluminium is much cheaper, however the reduced operational costs due to weight savings mean that GLARE has a lower total life-cycle cost.

Question 5

Describe the first manufacturing technique for GLARE fueselage panels.

Answer 5

Self-forming Technique:

• Lay-up of prepreg fibre reinforced plastic (FRP) and aluminium sheets onto a lay-up tool/mould with adhesive between layers of bonding.
• Prepreg FRP is laid onto tooling with specific fibre directionality.
• Cured in an autoclave to cure the thermoset plastic.
• All of this takes place in one single cycle.
• FRP and metal layers are forced against the mould under pressure (6 - 11 bar). Layup is required because the low failure strain of the fibres makes stress forming and bending unsuitable.
• Aluminium sheets are elastically deformed during this process. This is just one source of residual stresses in the structure that can result in deformation after moulding. Thermal shrinkage is another source. this needs to be accounted for in the mould design so that the final shape is within the desired tolerances.

Question 6

Describe the second manufacturing technique for GLARE fueselage panels.

Answer 6

Trimming and Cutting:

The final desired shape is then achieved using CNC machining or water jet cutting (e.g. windows).

Question 7

List two suitable methods of inspection.

Answer 7

Visual Inspection.

Eddy Current Testing.