33
2
4. Low Coefficient of Thermal Expansion (CTE)—Composites
have a low coefficient of thermal expansion (CTE); therefore,
they don’t cause any problems with dimensional stability on
the application of temperature at or below their T g . Most of
the reinforcing fibres have a low (but positive) linear coefficient of thermal expansion. Carbon fibre has negative linear
CTE, but this shrinkage is compensated in composites due to
their positive linear coefficient of thermal expansion of
polymeric matrix. Mostly, composites have negative values of
CTE, as shown in . Table 2.2.
5. Increased Mechanical Damping—Damping in structures is
commonly provided by viscoelastic materials. The damping
characteristic of composites is substantial due to a viscoelastic
matrix. The interfaces and viscoelasticity of the matrix in
composites increase the damping capacity of composites with
negligible decrease—if any—of the storage modulus.
Significant damping capacity along with high strength and
stiffness is desired in composite structures. Composites
generally offer relatively high levels of damping. Furthermore,
the damping often can be tailored to desired levels by using
suitable raw materials and processing.
6. Corrosion Resistance—Composites are made of polymeric
matrices and reinforcing inorganic or organic fibres. The
matrix is the outermost surface of the composites, and it is
corrosion resistant. Therefore, they resist damage from the
. Table 2.1 Comparison of HDT between composites and their matrix resin [18]
Serial no.
Material
Deflection temperature at 0.46 MPa (°C)
Deflection temperature
at 1.8 MPa (°C)
Melting
point (°C)
1.
Abs
98
88
–
2.
ABS + 30% glass fibre
150
145
–
5.
Nylon 6
160
60
220
6.
Nylon 6 + 30% glass fibre
220
200
220
7.
Polyethylene terephthalate (PET)
70
65
250
8.
PET +30% glass fibre
250
230
250
9.
Polypropylene
100
70
160
10.
Polypropylene +30% glass fibre
170
160
170
. Table 2.2 CTE of composites [19]
Serial no.
Material
CTE (10 −6 /°C)
1.
Carbon/epoxy
−0.002
2.
Glass/epoxy
−0.414
3.
Graphite/epoxy
−1.051
2.1 · Advantages of Polymeric Composites
2
4. Low Coefficient of Thermal Expansion (CTE)—Composites
have a low coefficient of thermal expansion (CTE); therefore,
they don’t cause any problems with dimensional stability on
the application of temperature at or below their T g . Most of
the reinforcing fibres have a low (but positive) linear coefficient of thermal expansion. Carbon fibre has negative linear
CTE, but this shrinkage is compensated in composites due to
their positive linear coefficient of thermal expansion of
polymeric matrix. Mostly, composites have negative values of
CTE, as shown in . Table 2.2.
5. Increased Mechanical Damping—Damping in structures is
commonly provided by viscoelastic materials. The damping
characteristic of composites is substantial due to a viscoelastic
matrix. The interfaces and viscoelasticity of the matrix in
composites increase the damping capacity of composites with
negligible decrease—if any—of the storage modulus.
Significant damping capacity along with high strength and
stiffness is desired in composite structures. Composites
generally offer relatively high levels of damping. Furthermore,
the damping often can be tailored to desired levels by using
suitable raw materials and processing.
6. Corrosion Resistance—Composites are made of polymeric
matrices and reinforcing inorganic or organic fibres. The
matrix is the outermost surface of the composites, and it is
corrosion resistant. Therefore, they resist damage from the
. Table 2.1 Comparison of HDT between composites and their matrix resin [18]
Serial no.
Material
Deflection temperature at 0.46 MPa (°C)
Deflection temperature
at 1.8 MPa (°C)
Melting
point (°C)
1.
Abs
98
88
–
2.
ABS + 30% glass fibre
150
145
–
5.
Nylon 6
160
60
220
6.
Nylon 6 + 30% glass fibre
220
200
220
7.
Polyethylene terephthalate (PET)
70
65
250
8.
PET +30% glass fibre
250
230
250
9.
Polypropylene
100
70
160
10.
Polypropylene +30% glass fibre
170
160
170
. Table 2.2 CTE of composites [19]
Serial no.
Material
CTE (10 −6 /°C)
1.
Carbon/epoxy
−0.002
2.
Glass/epoxy
−0.414
3.
Graphite/epoxy
−1.051
2.1 · Advantages of Polymeric Composites