Question

Do some internet research on the properties of composite materials. a) Compare the tensile strength of a typical glass fibre reinforced polymer with the tensile strength of a carbon fibre reinforced polymer. Make sure you the fibre lay-up is the same in your two examples and that you record what that is in your answer. Use data tables from reputable engineering or scientific web pages or material suppliers only and cite your reference(s).

Answer:....................................................................................................................... ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. b) Write a few lines about metal-matrix composites and how their properties compare with polymer based composites.

Answer:....................................................................................................................... ................................................................................................................................. ................................................................................................................................. .................................................................................................................................

Answer 1

Composites, known also as fibre-reinforced plastics (FRP), are defined as materials which are a combination of reinforcements and matrix. Neither of these are well suited for construction purposes on their own , but when combined result in a very strong and rigid material.

Properties of Composite materials :

1. HIGH STRENGTH TO WEIGHT RATIO:  Fibre composites are extremely strong for their weight.A carbon fibre laminate has a stiffness of many times that of mild steel of the same thickness, increased ultimate strength, yet only be less than 1/4 of it's weight.

2.LIGHTWEIGHT:  A standard Fibreglass laminate has a specific gravity in the region of 1.5, compared to Alloy of 2.7 or steel of 7.8

3.FIRE RESISTANCE: The ability for composites to withstand fire has been steadily improving over the years. There is two types of systems to be considered:

Fire Retardant - Are self extinguishing laminates, usually made with chlorinated resins and additives such as Antimony trioxide. These release CO2 when burning so when the flame source is removed, the self extinguish.

Fire Resistant - More difficult and made with the likes of Phenolic Resins. These are difficult to use, are cured with formaldehyde, and require a hi degree of post curing to achieve true fire resistance.

4.ELECTRICAL PROPERTIES: ​Fibreglass Developments Ltd produced the Insulator Support straps for the Tranz Rail main trunk electrification. The straps, although only 4mm thick, meet the required loads of 22kN, as well as easily meeting  insulation requirements.

5.CHEMICAL & WEATHERING RESISTANCE: Composite products have good weathering properties and resist the attack of a wide range of chemicals.

6.COLOUR: ​Almost any shade of any colour can be incorporated into the product during manufacture by pigmenting the gelcoat used. Costs are therefore reduced by no further finishing or painting. Soluble dyes can be used if a translucent product is desired but dark colours are not recommend.

7.TRANSLUCENCY:  Polyester resins are widely used to manufacture translucent mouldings and sheets. Light transmission of up to 85% can be achieved.

8.DESIGN FLEXIBILITY: Because of the versatility of composites, product design is only limited by your imagination.

9.LOW THERMAL CONDUCTIVITY: Fibreglass Developments has been involved in the development and production of specialized meat containers which maintain prime cuts of chilled meat at the correct temperature for Export markets.

10.MANUFACTURING ECONOMY: They are manufactured using the RTM process, with special reinforcing and foam inserts. Fibreglass is an ideal material for producing items of this type for many reasons, including being very economical.

Because of its versatile properties, fibreglass can be used in many varied applications.

A. Comparison the tensile strength of a typical glass fibre reinforced polymer with carbon fibre reinforced polymer. [ 1]

Tensile Strength of GFRP(MPa)	Tensile Strength of CFRP(MPa)
orientation 0°, Single Layer= 30.9	orientation 0°, Single Layer= 45.4
orientation 0°, Double Layer = 38.4	orientation 0°, Double Layer= 50.5

B. Metal matrix composites

(i) A metal matrix composite (MMC) is composite material with at least two constituent parts, one being a metal necessarily, the other material may be a different metal or another material, such as a ceramic or organic compound. When at least three materials are present, it is called a hybrid composite. An MMC is complementary to a cermet.

(ii) MMCs are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. For example, carbon fibers are commonly used in aluminium matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminium to generate a brittle and water-soluble compound Al₄C₃ on the surface of the fibre. To prevent this reaction, the carbon fibres are coated with nickel or titanium boride

Metal Matrix Composites	Polymer Composites
superior yield strength and tensile strength	High tensile streng
high thermal resistance	High stiffness
better conductivity	High Fracture Toughness
better chemical and moisture resistance	Good abrasion resistance
better corrosion resistance	Good corrosion resistance
can be used over a wide temperature range	Low cost

References

[1] https://aip.scitation.org/doi/abs/10.1063/1.4945487