Composite Materials – Assignment 4Evaluate Applications of Composites

You are required to investigate the application of a composite material for a specific product in one of the following market sectors.

a) Automotiveb) Aerospacec) Marined) Leisure

For this assignment I will use my project as my product. This was made of a composite material and is an aerospace component and should suit the purpose of the assignment.

Introduction

The Lynx Restoration Project is an apprentice run project where we take an old lynx and renovate it to athstetically accurate state from when it used to fly. The project I am working on is particularly special because we have the World Speed Record Lynx; this Lynx Helicopter broke the fastest speed record for a helicopter on 11th August 1986 achieving a speed of 400.87kph / 249.10mph and has held this record to this day.

One of the particular parts I was assigned to work on and the one I am using for my HNC project was the Intermediate Gear Box (IGB) Smoothing Fairing. In an ideal world we would have tried to source the part from the previous locations of the aircraft to see if they still had it but we have had no luck.The other alternative is to design one ourselves using the design instructions and engineering drawings made by the original project team back in the 1980’s. Doing it this way meant that I could look into new methods and ways of making the part compared to any old or redundant methods used to make the original part.

The IGB smoothing fairing is a unique part designed specifically for the world speed record attempt. As shown in the figure below the smoothing fairing is placed over the main IGB fairing to cover an air vent that cools the IGB, the smoothing fairing may increase temperature of the gearbox but it also dramatically increases the aerodynamics of this part of the aircraft.

For the specified product you must:

1 – Compare and contrast the reasons for using a Composite material as an alternative to conventional material.

Composite provide many benefits than conventional materials for example:

Greater design freedom

For my product the shape I had to manufacture had complex curvature that would be difficult to produce using a metal of conventional material, using a composite on a mould tool gave me the flexibility to make the shape I desired.

Lower system cost

Overall using a composite material decreases tooling cost and could reduce material cost. This makes the whole process generally cheaper. For my product it was only a one off piece, this meant producing a complicated piece of tooling to form the metal into the shape I wanted and to perform all the other processes that would be required could be quite expensive and un-economical towards my budget.With a composite material we ended up making a foam mould and laid the material straight onto the aircraft rather than separately manufacturing the part on machines.

Location of the IGB Smoothing Fairing

Concept Model of Foam Mould Insert for Composite Lay-up

Weight reduction potential

The main benefit of most composites is there weight (or strength), for my product the weight wasn’t a massive issue as the aircraft it’s being used on isn’t going to fly. But I still needed to keep it roughly the same weight as the original to keep it authentic.

Excellent strength to weight ratio

The weight to strength ratio as I mentioned above is one of the bigger advantages in composites. When the fibres are placed in the most effective orientation this can produce massive strength increases in comparison to their weight in a certain direction.

Excellent dimensional stability

Composites have a good tendency to not alter in shape when put under various extreme temperatures which make them quite resistant to fatigue .

Excellent corrosion resistance

My part will be used for museum exhibits so there isn’t going to be a great deal of corrosion but being a composite this will at least remove the requirement to maintain it as much.

Lower tooling cost

As said above tooling cost is greatly reduced specifically for my product. All that was involved was the one foam mould that was bonded underneath and then composite material lay up on top.

Excellent thermal properties

Electrical insulation Potential to integrate electrical equipment

2. Justify the use of a Composite material in terms of the technical benefits, achievements and financial considerations

Considering the technical benefits listed above in relation to my product other technical and financial benefits on using a composite material would be:

Overall Structural Weight %

This example of a ship hull show shows the maintenance cost of two separate materials:

Crashworthiness –

Carbon Fibre Breaking Point

Steel Breaking Point

Metal is ductile

Dependant on the design, composite material is generally higher in strength but brittle compared to a metal as shown in the graph below. (NOT TO SCALE)

Damage Tolerance

Generally higher than metals hardly any effects from scratches, although…

Robustness

Composites are not as tough as metals and could become delaminated (harder to notice) opposed to a dent in metal.

Less robust in thin arrangements

You can get barely visible impact damage (BVID) on composite partsBVID = anything you can see from 3-5 ft away

Repair

Composite patches are much easier to make than metallic; with metallic patches the machining of the 3d object needed for the repair could be tricky and costly, whereas composite plies can be more easily formed.

Supply Issues

Composites are harder to obtain because composite materials don’t come to any standard, unlike metal where you can request a certain type or grade or quality etc.

WHL have to make their own standards for composite materials. This is more expensive to do than simply obtaining metals at the correct standards.

Electrical

Carbon conducts, composite parts must take account of a lightning strike.

An earth has to be built into composite materials I.e. Glass fibre materials where as metals already conduct and so do not require this.

Cost

More than Aluminium, Carbon = approximately £20/m2 for 5000 thickness.

Weight

For the same size components, composite materials are often considerably lighter than their metallic counterparts and if layed up in the correct way can be just as strong.

3. Identify the factors that must be considered in adopting your choice of Composite material for the environment in which the product must perform.

Environmental Effects

Sunlight could damage composite, paint over the surface solves this problem.

Epoxy resins absorb moisture (fairly slowly).

It is difficult to simulate moisture tolerance for composite material in a sensible timescale.

Metals corrode, composites don’t. Most metals would corrode and lose more of their strength than a composite material absorbing moisture

Composites are more expensive to qualify but could be worth the cost in the long run if the material lasts longer.

In their unprocessed form, thermoset resins pose the greatest risk. The primary hazard comes from volatile organic compounds (VOCs) given off by the resins. New government regulations, both in the U.S. and Europe, significantly limit personnel exposure to VOCs. Resins can also cause skin damage and allergic reactions. Thermoplastic resins are handled in solid form and pose little risk. Excess or waste materials are cured, rendering them inert, before disposal. The solvents used in processing plastics, however, remain hazardous both in handling and in disposal.

Fibers are relatively benign, but carbon and glass fibers can cause skin and respiratory irritation. Fibers are too large to be inhaled, so irritation is limited to the upper respiratory tract. Carbon fibers are conductive, so electrical and electronic equipment should be protected from contamination. Adequate dust control should be used when machining composites of any type.

4. Review the current status and predicted developments in Composite material applications in the market sector you have chosen.

Currently in Aerospace composites are making a big impact on the state of aircraft, mainly from a weight and strength point. Composite parts have primarily been small components that are not structurally critical.Recently composites have advanced and are now being used as structural panels and many other components on various aircraft. The picture above shows a Hornet as you can see the red shading indicates the use of Carbon Epoxy for improved Toughness and high strength/durability.

The picture above is similar to the Hornet but shows the use of materials on the EH101 Helicopter, this is a good example of the combination of metallic and composite materials used. The cockpit and tail structural sections are mainly composite but the fuselage is Aluminum Lithium skins with Honeycomb cores.

In the future composites will continue to develop and progress to provide specific properties for the application they are to be used in. It would be ignorant to say that composites will not be a

major part of the future of engineering. The progression in the past century proves this. For example the full airframe of the NH90 aircraft is fully composite.

Bibliography

www.mitras.co.uk

Composites in Aerospace Applications – By Adam Quilter, Head of Strength Analysis Group, ESD International

Tooley & Dingle – HNC Book