157
6
? Example 6.3 Calculate Poisson’s ratio of a talc-filled HDPE
composite. The modulus and ϕ f of talc is 12 GPa and 0.2,
respectively.
v Answer
E E
c
p
f
f
GPa
=
+
+
(
)
=
+
× +
×
(
)
=
1 2 5
14 1
12 1 2 5 2 14 1 0 8
24 78
.
.
.
.
.
.
φ
φ
E E
v
v
p
p
c
p
f
f
/
= +
−
( )
−
−
1
1
10
1
15
8
φ
φ
V p = 0 68
.
In thermoplastic composites, consolidation and bonding are two
important factors to obtaining a good composite. The first step
towards this is the intimate contact between the reinforcement and
the matrix. The second is autohesion (automatic + adhesion/cohesion). The following models describe the effects of the processing
variables (time, temperature, and pressure) on intimate contact and
autohesion.
6.4.1 Intimate Contact
Initially, at the time of placement of reinforcement and matrix are
placed together, there are gaps (such as air pockets) between them
prior to the application of heat and pressure. Even at high temperatures, the viscosity of thermoplastics is too high to produce the
desired degree of flow along the interface. Therefore, thermoplastic
matrix composites must actually be deformed to produce intimate
contact between adjacent surfaces. Equations used for intimate
contact are
D
b w b
ic =
+
(
)
/ 0 0
(6.5a)
V a b ab
0
0 0
= =
(6.5b)
where
5 D ic = Degree of intimate contact
5 a 0 = Initial height of each rectangular element
5 a = Spontaneous heights of each rectangular element
5 b 0 = Initial width of each rectangular element
5 b = Spontaneous width of each rectangular element
5 w 0 = Initial distance between two elements
5 V 0 = Volume of each rectangular element
D
a a
w b
ic = +
0
0
0
1
/
/
(6.6)
6.4 · Thermoplastic Composites
6
? Example 6.3 Calculate Poisson’s ratio of a talc-filled HDPE
composite. The modulus and ϕ f of talc is 12 GPa and 0.2,
respectively.
v Answer
E E
c
p
f
f
GPa
=
+
+
(
)
=
+
× +
×
(
)
=
1 2 5
14 1
12 1 2 5 2 14 1 0 8
24 78
.
.
.
.
.
.
φ
φ
E E
v
v
p
p
c
p
f
f
/
= +
−
( )
−
−
1
1
10
1
15
8
φ
φ
V p = 0 68
.
In thermoplastic composites, consolidation and bonding are two
important factors to obtaining a good composite. The first step
towards this is the intimate contact between the reinforcement and
the matrix. The second is autohesion (automatic + adhesion/cohesion). The following models describe the effects of the processing
variables (time, temperature, and pressure) on intimate contact and
autohesion.
6.4.1 Intimate Contact
Initially, at the time of placement of reinforcement and matrix are
placed together, there are gaps (such as air pockets) between them
prior to the application of heat and pressure. Even at high temperatures, the viscosity of thermoplastics is too high to produce the
desired degree of flow along the interface. Therefore, thermoplastic
matrix composites must actually be deformed to produce intimate
contact between adjacent surfaces. Equations used for intimate
contact are
D
b w b
ic =
+
(
)
/ 0 0
(6.5a)
V a b ab
0
0 0
= =
(6.5b)
where
5 D ic = Degree of intimate contact
5 a 0 = Initial height of each rectangular element
5 a = Spontaneous heights of each rectangular element
5 b 0 = Initial width of each rectangular element
5 b = Spontaneous width of each rectangular element
5 w 0 = Initial distance between two elements
5 V 0 = Volume of each rectangular element
D
a a
w b
ic = +
0
0
0
1
/
/
(6.6)
6.4 · Thermoplastic Composites