Civil Engineering Reference
In-Depth Information
TABLE 3.11
Typical Mechanical Properties for Ultrahigh-Modulus
Graphite/Epoxy Unidirectional Composites with
V
f
= 0.6
Elastic Constants
GPa
10
6
psi
Longitudinal modulus,
E
L
290
42
Transverse modulus,
E
T
6.2
0.9
Axial shear modulus,
G
LT
4.8
0.7
Poisson's ratio,
v
LT
(dimensionless)
0.25
Strength Properties
MPa
10
3
psi
620
90
Longitudinal tension,
F
L
tu
Longitudinal compression,
F
L
cu
620
90
21
3
Transverse tension,
F
T
tu
170
25
Transverse compression,
F
T
cu
In-plane shear,
F
L
su
60
9
Interlaminar shear,
F
isu
60
9
Ultimate Strains
(%)
0.2
Longitudinal tension, ∈
tu
0.2
Longitudinal compression, ∈
cu
Transverse tension, ∈
tu
0.3
Transverse compression, ∈
cu
2.8
In-plane shear, γ
LT
0.6-4
u
Density, kg/m
3
(lb/in.
3
)
1.70 × 10
3
(0.061)
Source:
Courtesy of Zweben (1989).
The ultimate strain here is reported by the manufacturer.
For the other three coupons,
2
2
A
=× ×=
20.043
10.086in (55.48
mm
)
f
6.828
0.086
f
=
=
79.4k
si
(547.75
MPa
)
fu
f
79.4
0.022
fu
fu
E
=
ε
=
=
3609k 24.9)
si
GPa
f
.
The ultimate strain here is reported by the manufacturer.
It is evident that the two sets of coupons have almost the same net fiber
strength and modulus. This is why net fiber properties are more con-
sistent to use in strengthening than laminate properties for wet lay-up
applications. Another way to obtain consistent results between the two
sets of coupons is to compute the average FRP strength per unit width
of the laminate:
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