21
1
Their stress–strain curves are linearly elastic to the point of failure
by rupture. Polymeric composites may be moulded into any intricate shape, and their properties can be tailored to the specific
requirements by careful selection of the fibre, matrix, fibre configuration (short, long, strength, woven, braided, laminated, etc.), and
fibre surface treatment.
1.7.1 Physical and Mechanical Behaviour
Polymeric composites have high specific mechanical properties.
The specific strength (strength-to-density ratio) and specific modulus (modulus-to-density ratio) of polymeric composites are
much higher than those of conventional materials, such as metals.
The weight savings due to high specific mechanical properties of
polymeric matrix composites make all types of vehicles (such as
aircrafts, rockets, automobiles, etc.) higher in fuel efficiency and
with a higher capacity to carry a pay load. Typical properties of
unidirectional (UD) polymeric composites are given in
. Table 1.10.
1.7.2 Thermal Behaviour
The thermal performance of polymeric composite largely depends
upon the type and chemical nature of the resin matrix and the curing process. Composites present high thermal anisotropy in both
along-the-fibre and perpendicular-to-fibre directions. The thermal
conductivity ratio between these two directions can vary between
40 and approximately 130. In a unidirectional laminate, the in- plane
direction is generally referred to as the along-the-fibre direction, and
the through thickness direction is often the perpendicular-to-fibre
direction. In many applications, heat removal is essential in both
in-plane and through-thickness directions for effective heat dissipa. Table 1.10 Typical physical and mechanical properties of unidirectional (UD) polymeric composites [10–12]
Serial no.
UD composites
Density
(g/cm 3 )
Tensile strength
(MPa)
Tensile
modulus (GPa)
Shear strength
(GPa)
Poisson’s
ratio
1.
Carbon/epoxy
(V f = 60%)
1.5
1600
224
0.06
0.28
2.
Boron/epoxy
(V f = 50%)
2.0
1500
148
0.07
0.23
3.
Glass/epoxy
(V f = 45%)
1.9
1300
41
0.07
0.26
4.
Kevlar 49/epoxy
(V f = 60%)
1.4
1380
58
0.03
0.34
Note: V f is volume fraction of fibres
1.7 · Properties of Polymeric Composites
1
Their stress–strain curves are linearly elastic to the point of failure
by rupture. Polymeric composites may be moulded into any intricate shape, and their properties can be tailored to the specific
requirements by careful selection of the fibre, matrix, fibre configuration (short, long, strength, woven, braided, laminated, etc.), and
fibre surface treatment.
1.7.1 Physical and Mechanical Behaviour
Polymeric composites have high specific mechanical properties.
The specific strength (strength-to-density ratio) and specific modulus (modulus-to-density ratio) of polymeric composites are
much higher than those of conventional materials, such as metals.
The weight savings due to high specific mechanical properties of
polymeric matrix composites make all types of vehicles (such as
aircrafts, rockets, automobiles, etc.) higher in fuel efficiency and
with a higher capacity to carry a pay load. Typical properties of
unidirectional (UD) polymeric composites are given in
. Table 1.10.
1.7.2 Thermal Behaviour
The thermal performance of polymeric composite largely depends
upon the type and chemical nature of the resin matrix and the curing process. Composites present high thermal anisotropy in both
along-the-fibre and perpendicular-to-fibre directions. The thermal
conductivity ratio between these two directions can vary between
40 and approximately 130. In a unidirectional laminate, the in- plane
direction is generally referred to as the along-the-fibre direction, and
the through thickness direction is often the perpendicular-to-fibre
direction. In many applications, heat removal is essential in both
in-plane and through-thickness directions for effective heat dissipa. Table 1.10 Typical physical and mechanical properties of unidirectional (UD) polymeric composites [10–12]
Serial no.
UD composites
Density
(g/cm 3 )
Tensile strength
(MPa)
Tensile
modulus (GPa)
Shear strength
(GPa)
Poisson’s
ratio
1.
Carbon/epoxy
(V f = 60%)
1.5
1600
224
0.06
0.28
2.
Boron/epoxy
(V f = 50%)
2.0
1500
148
0.07
0.23
3.
Glass/epoxy
(V f = 45%)
1.9
1300
41
0.07
0.26
4.
Kevlar 49/epoxy
(V f = 60%)
1.4
1380
58
0.03
0.34
Note: V f is volume fraction of fibres
1.7 · Properties of Polymeric Composites