1.0 INTRODUCTION
Various composite materials have been widely used in aerospace engineering owing not only to a
broad range of physicomechanical and chemical characteristics but also capability of directed
change of their properties in compliance with structural assignment. Today, studies of composite
materials belonging to three main categories which are dispersion, particle-strengthened and
fibre-reinforced materials. Whatever the material, a composite is formed by a matrix of low
modulus material and reinforcing elements with higher strength and stiffness. Particular
emphasis is placed on the development and study of fibrous composite materials. Further
increase of the weight efficiency of flying vehicle structures and improvement of their
performance are associated precisely with the application.
For a long time, aviation firms and scientific research agencies have been making intense
investigations of composite materials application in the structures of flying vehicles. A large
number of units made of polymer based materials have been developed and subjected to ground
tests, installed in operational items and run successfully for a long time. The accumulated data on
the strength and operating characteristics of composite structures confirm the possibility of
ensuring static strength, useful life and required stiffness with substantial reduction of the
structure’s weight. The created structures demonstrate the practical implementation of substantial
structure weight reduction.
Since 1986, the use of high-performance polymer-matrix fiber composites in aircraft structures
has grown steadily, although not as dramatically as predicted at that time. This is despite the
significant weight reduction and other advantages that these composites can provide. The main
reason of slowing down anticipation take up is due to the high cost of aircraft components made
of composites compared to similar structures with metal, mainly aluminum, alloys. Others
include high cost of certification, new components adjusting, properties and temperature
limitations. Thus, metals will continue to be favored for many airframes applications.
2
,The growth in the use of composites in the airframes in selected aircraft is illustrated in Figure
1.1. However, despite this growth, the reality is, most airframes including engines will continue
to be a mix of materials. See Figure 1.2. These will include composites of various types and a
range of metal alloys, the balance depending on structural and economic factors.
Figure 1.1: Growth of composites in aircraft industry
Figure 1.2: Materials used in Boeing 787 in general
3
, 2.0 COMPOSITE MATERIALS IN AIRCRAFT INDUSTRY
Among the first uses of modern composite materials was about 40 years ago when boron-
reinforced epoxy composite was used for the skins of the empennages of the U.S. F14 and F15
fighters (Adam, 2012). Initially, composite materials were used only in secondary structure, but
as knowledge and development of the materials has improved, their use in primary structure such
as wings and fuselages has increased. Most famous all time composite materials used in the
aerospace and other industries are carbon and glass-fiber-reinforced plastic (CFRP and GFRP
respectively) which consist of carbon and glass fibers, both of which are stiff and strong for their
density, but brittle. In a polymer matrix, the materials are tough but neither particularly stiff nor
strong. Very simplistically, by combining materials with complementary properties in this way, a
composite material with most or all of the benefits (high strength, stiffness, toughness and low
density) is obtained with few or none of the weaknesses of the individual component materials.
Modern composites rely on matrix that can be molded into complex shapes. In earlier
applications Bakelite, a liquid phenolic resin combined with weakly reinforcement like sodas,
paper or cloth had been used for aircraft. However, these phenolic resin composites had some
serious limitations in terms of strength. They are particularly brittle and managed to pick a slot
usage to make small parts like insulators and control knobs inside the aircraft. In 1930s, Loans
Corning developed fiber glass composites. Early fiber glass still used phenolic resin, so the
composites were still brittle but they were quite strong. This strong and moldable fiber glass was
not suitable for aircraft parts but was perfect for creating parts. Duplex aircraft company used
fiberglass composites as forming die tools to produce prototype metal aircraft parts. At the
approach of second world war, several advances occurred in material science including polymer
chemistry. New synthetic resins were then developed and brittle matrix problem has been
eliminated. This new generation of composites was very deafly.
4
Various composite materials have been widely used in aerospace engineering owing not only to a
broad range of physicomechanical and chemical characteristics but also capability of directed
change of their properties in compliance with structural assignment. Today, studies of composite
materials belonging to three main categories which are dispersion, particle-strengthened and
fibre-reinforced materials. Whatever the material, a composite is formed by a matrix of low
modulus material and reinforcing elements with higher strength and stiffness. Particular
emphasis is placed on the development and study of fibrous composite materials. Further
increase of the weight efficiency of flying vehicle structures and improvement of their
performance are associated precisely with the application.
For a long time, aviation firms and scientific research agencies have been making intense
investigations of composite materials application in the structures of flying vehicles. A large
number of units made of polymer based materials have been developed and subjected to ground
tests, installed in operational items and run successfully for a long time. The accumulated data on
the strength and operating characteristics of composite structures confirm the possibility of
ensuring static strength, useful life and required stiffness with substantial reduction of the
structure’s weight. The created structures demonstrate the practical implementation of substantial
structure weight reduction.
Since 1986, the use of high-performance polymer-matrix fiber composites in aircraft structures
has grown steadily, although not as dramatically as predicted at that time. This is despite the
significant weight reduction and other advantages that these composites can provide. The main
reason of slowing down anticipation take up is due to the high cost of aircraft components made
of composites compared to similar structures with metal, mainly aluminum, alloys. Others
include high cost of certification, new components adjusting, properties and temperature
limitations. Thus, metals will continue to be favored for many airframes applications.
2
,The growth in the use of composites in the airframes in selected aircraft is illustrated in Figure
1.1. However, despite this growth, the reality is, most airframes including engines will continue
to be a mix of materials. See Figure 1.2. These will include composites of various types and a
range of metal alloys, the balance depending on structural and economic factors.
Figure 1.1: Growth of composites in aircraft industry
Figure 1.2: Materials used in Boeing 787 in general
3
, 2.0 COMPOSITE MATERIALS IN AIRCRAFT INDUSTRY
Among the first uses of modern composite materials was about 40 years ago when boron-
reinforced epoxy composite was used for the skins of the empennages of the U.S. F14 and F15
fighters (Adam, 2012). Initially, composite materials were used only in secondary structure, but
as knowledge and development of the materials has improved, their use in primary structure such
as wings and fuselages has increased. Most famous all time composite materials used in the
aerospace and other industries are carbon and glass-fiber-reinforced plastic (CFRP and GFRP
respectively) which consist of carbon and glass fibers, both of which are stiff and strong for their
density, but brittle. In a polymer matrix, the materials are tough but neither particularly stiff nor
strong. Very simplistically, by combining materials with complementary properties in this way, a
composite material with most or all of the benefits (high strength, stiffness, toughness and low
density) is obtained with few or none of the weaknesses of the individual component materials.
Modern composites rely on matrix that can be molded into complex shapes. In earlier
applications Bakelite, a liquid phenolic resin combined with weakly reinforcement like sodas,
paper or cloth had been used for aircraft. However, these phenolic resin composites had some
serious limitations in terms of strength. They are particularly brittle and managed to pick a slot
usage to make small parts like insulators and control knobs inside the aircraft. In 1930s, Loans
Corning developed fiber glass composites. Early fiber glass still used phenolic resin, so the
composites were still brittle but they were quite strong. This strong and moldable fiber glass was
not suitable for aircraft parts but was perfect for creating parts. Duplex aircraft company used
fiberglass composites as forming die tools to produce prototype metal aircraft parts. At the
approach of second world war, several advances occurred in material science including polymer
chemistry. New synthetic resins were then developed and brittle matrix problem has been
eliminated. This new generation of composites was very deafly.
4
