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Application of composite materials in aviation.



Abstract: At the end of the thirties of the last century, the introduction of aluminium replacing wood and steel as material for the construction of aircraft caused changes in the very design of the aircraft as well as modifications in their manufacturing procedure. Today, we are witnessing a similar process, composite materials slowly taking over the role of aluminium, new design solutions whose implementation made possible by the use of new materials is sweeping away the old solutions.

Key words: usage of composite materials, lifecycle of aircraft, costs, exhaust gases polution

1.INTRODUCTION

The increase in air traffic volume has brought to increasing emissions of exhaust gases, fuel consumption and increase in transport charges. In order to stop this process it is necessary to improve the aircraft performances, increase the utilization coefficient utilization coefficient

in terms of oxygen transport in the blood this coefficient expresses the proportion of oxygen in the blood which diffuses into tissues as it passes through the capillaries.
 and to prolong pro·long  
tr.v. pro·longed, pro·long·ing, pro·longs
1. To lengthen in duration; protract.

2. To lengthen in extent.
 the lifecycle of the very aircraft.

Aircraft manufacturers have been forced to reduce the costs of development, production and maintenance of the aircraft. In order to achieve these goals, the designers were forced to substitute the classical materials by those that enable faster production, reduce mass, reduce the maintenance requirements and prolong the lifecycle of the aircraft. As a solution, high-quality composite materials have been used.

2.DISCUSSION

Composite materials are materials obtained by combining two or more substances which feature different properties, and in which every substance retains its chemical integrity. By rough classification, the composite materials can be divided into basic composites, layered substances (laminates and panels) and interwoven in·ter·weave  
v. in·ter·wove , in·ter·wo·ven , inter·weav·ing, inter·weaves

v.tr.
1. To weave together.

2. To blend together; intermix.

v.intr.
 structures.

In order to compare the material properties, the basic composites are usually divided, according to according to
prep.
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

3.
 the matrix, into metal, polymer and ceramic. The exception from this rule are the long-fibre composites which are usually qualified according to the substance of which they are made. The latter two groups will be discussed in more detail further in the text because they form the major part of the total volume of composites used in aircraft manufacture.

The advantages of composite materials compared to metals in the aircraft construction are: longer lifecycle due to higher material fatigue resistance, corrosion resistance, easier maintenance, higher resistance to fire, easier material processing, possibility of designing more complex shapes, and lower specific mass of the material.

The drawbacks of the composite materials are indicated in the higher unit price of their manufacture compared to steel, wood or aluminium (2-5 times).

The aircraft fuselage may be made of many different materials such as e.g. wood, fabric, aluminium and other metals, as well as composites. In the construction of today's aircraft several materials are mainly used, mostly aluminium and its alloys, titanium titanium (tītā`nēəm, tĭ–) [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.88; m.p. 1,675°C;; b.p. 3,260°C;; sp. gr. 4.54 at 20°C;; valence +2, +3, or +4.  and composites. In selecting the material for a certain part of the structure, the designer makes the choice by selecting the lightest material with adequate properties. However, there are some restrictions here, and in the construction of aircraft, first of all for general and commercial purpose, these usually refer to finances.

Although it may seem so at the first glance, composite materials are no novelty Novelty is the quality of being new. Although it may be said to have an objective dimension (e.g. a new style of art coming into being, such as abstract art or impressionism) it essentially exists in the subjective perceptions of individuals.  in the construction of aircraft. Already in the 50s of the last century fibreglass was used in the construction of Boeing 707 and it occupied about 2% in the total volume of the used materials.

The first major use of composite materials in the construction of military aircraft occurred in case of aircraft F-14 Tomcat A popular Java servlet container from the Apache Jakarta project. Tomcat uses the Jasper converter to turn JSPs into servlets for execution. Tomcat is widely used with the JBoss application server. For more information, visit http://jakarta.apache.org/tomcat. See Jakarta and JBoss. . In 1981 British Aerospace--McDonnell Douglas manufactured AV-8B Harrier harrier, breed of dog
harrier, breed of medium-sized hound whose origin is obscure but whose existence in England dates from the 13th cent. It stands from 19 to 21 in. (48.3–53.3 cm) high at the shoulder and weighs from 40 to 50 lb (18.1–22.
 in whose structure the composite materials participated with 25 percent. Almost one third of the modern military aircraft such as e.g. F-22 Raptor and Eurofighter is made of composite materials.

Due to the expensiveness of composite material composite material or composite, any material made from at least two discrete substances, such as concrete. Many materials are produced as composites, such as the fiberglass-reinforced plastics used for automobile bodies and boat hulls, but the  manufacture, their greater use in commercial aviation came at a later date. Thus e.g. in the total volume of materials used to manufacture Boeing 777 composites account for 10%.

The increasing use of composites in the construction of aircraft has resulted also in new composite materials. Thus, in the manufacture of Airbus aircraft A-380, apart from other composites, the upper part of the fuselage will be made of Glare glare (glar) discomfort in the eye and depression of central vision produced when a bright light enters the field of vision, particularly when the eye is adapted to dark. It is direct g. . Glare is aluminium reinforced by glass fibres thus reducing the mass of aluminium, and at the same time improving its mechanical properties. The unit price of manufacturing Glare is somewhat lower than the one in the production of other composites since aluminium-production plants can be extensively used in the process of manufacturing Glare. In the construction of A380 aircraft the composites will account for 16 percent in the total volume of material, whereas their use will reduce the aircraft mass by 15 tonnes compared to completely metal structure. The weight of an entirely empty A380 will be about 170 tonnes.

[FIGURE 2 OMITTED]

Neck and neck with Airbus in the use of composites in the construction of commercial aircraft is Boeing with its 7E7.

3.CONCLUSION

In the construction of aircraft today we find solutions which would be almost impossible to realize were it not for the use of composite materials. As example the aircraft Gruman X-29 and Sukhoi S-27 Berkut may be mentioned. They have wings in the form of reverse arrow and in their construction from materials such as aluminium they get deformed de·formed
adj.
Distorted in form.
 due to high loads in single flight phases.

In 2000, research started in the field of using composite materials in the construction of the bottom part of the fuselage. Major European aircraft manufacturers such as BAE systems BAE Systems

British manufacturer of aircraft, missiles, avionics, naval vessels, and other aerospace and defense products. BAE Systems was formed (1999) from the merger of British Aerospace (BAe) with Marconi Electronic Systems.
, Aerospitale Matra Airbus, Daimler Chrysler Aerospace Airbus and Alenia participated in the project together with numerous European research centres. Research was based on theoretical calculations as well as testing of the aircraft structure model in the laboratory. The achieved results are very promising, and a major share of composite materials in the construction of aircraft may be expected in the near future. Aircraft designed in this way will be lighter than today's aircraft of classical construction (made of metals) by about 35 percent.

In the construction of helicopters the things are moving even faster. Thus e.g. today there are helicopters that are almost completely made of composites (NH 90, Tiger Eurocopter EC 135).

Parallel with the integration of composite material application in the construction of the aircraft of today, their greater application appears also in the construction of aircraft engines. Thus, at the end of 2004, the General Electric Company started to test new Genx engines. The novelty in Genx engines consists in the fact that the same single jet engine except for the compressor compressor, machine that decreases the volume of air or other gas by the application of pressure. Compressor types range from the simple hand pump and the piston-equipped compressor used to inflate tires to machines that use a rotating, bladed element to achieve  blades, jet deflectors, etc. even the combustion chamber Combustion chamber

The space at the head end of an internal combustion engine cylinder where most of the combustion takes place. See Combustion
 is made of composite materials. This results in the longer lifecycle of the very engine as well as reduced maintenance costs. The installation of Genx engine is planned on the aircraft Boeing 7E7 Dreamliner. The installation of Genx engine is expected to reduce the total aircraft maintenance costs by about 10 percent. Furthermore, some design innovations in the engine itself reduce fuel consumption by about 40 percent as well as the exhaust emissions.

Although, considering the development, the application of aluminium and its alloys may be traced back to the very beginnings of aviation regarding the share in the total quantity of material used for the construction of aircraft, it still plays a crucial role. However, following the development of composite materials and the improvement of their production process, their declining unit price, it is to be expected that the significance of composites will increase in the near future in the construction of aircraft. Therefore, aircraft will soon be coming out of the workshops, for the production of which the major share in the overall materials used for their construction will be composite materials.

This will consequently mean a significant reduction in fuel consumption, exhaust gases and increase in the aircraft flight range and in the times to come with energy saving playing an important role, this will be of crucial significance. The fact should also be remembered that the use of such aircraft will result in maintenance savings due to the longer lifecycles of composite materials compared to aluminium and their alloys.

4.REFERENCES

K. Milos Miloš, prince of Serbia
Miloš or Milosh (Miloš Obrenović) (both: mĭ`lôsh ōbrĕ`nəvĭch) 
, I. Milos, D. Curepic: Composite Materials in the Construction of Transport Means, Promet-Traffic-Traffico (1), Zagreb, 2004,

P. K. Mallick and S. Newman: Composite Materials Tehnology-Proces and Properties, Carl Hanser Verlag, Munchen, 1990.

S. Rawal: Metal Matrix composites for Space Aplication, JOM JOM Journal of the Minerals, Metals & Materials Society
JOM Journal of Morphology
JOM Johnson O'Malley Program (Bureau of Indian Affairs)
JOM Journal of Orthomolecular Medicine
JOM Japanese Offshore Market
 53(4) 2001,

W. F. Powers: Adwanced Materials and Processes, May 2000.
Table 1. Comparison of properties of some materials

Typical properties of structural materials

Material       density        Tensile          Tensile
                              strength         modulus

               g/[cm.sup.3]   MPa              GPa

Pinewood       0.5             100              12
Al alloy       2.8             350              75
Ti alloy       4.5             800             110
Steel          7.8            1100             210
GRP            2.1             750              25
CFRP made
from HT
fibrts with
EP matrix      1.5             750              74
CFRP made
from HM
fibers with
EP matrix      1.6             600             100

Material       Shear          Spec.            Spec.
               modulus        strength         Young's
                                               modulus

               GPa            (MPa)/           (GPa)/
                              (g/[cm.sup.3])   (g/[cm.sup.3])

Pinewood       -              200              24
Al alloy       28             125              27
Ti alloy       42             178              24
Steel          81             140              27
GRP             6             360              12
CFRP made
from HT
fibrts with
EP matrix      19             500              50
CFRP made
from HM
fibers with
EP matrix      25             375              63

Fig. 1 Distribution of the use of single materials in the
construction of aircraft Boeing 777

others                   1%
aluminium               70%
composites              11%
titanium                 7%
steel                   11%

Note: Table made from pie chart.
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Author:Frankovic, I.; Lovric, I.; Rados, J.
Publication:Annals of DAAAM & Proceedings
Article Type:Technical report
Geographic Code:4EUAU
Date:Jan 1, 2005
Words:1553
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