Civil Engineering Reference
In-Depth Information
TABLE 3.14
GFRP Coupon Testing To Determine Laminate and Net-Fiber Properties
Average
Thickness
(in.)
Average
Thickness
(mm)
Rupture
Load
(kips)
Rupture
Load
(kN)
Width
(in.)
Width
(mm)
Ultimate
Strain
Specimen
GFRP-1
1.00
25.4
0.099
2.51
3.237
14.405
0.01507
GFRP-2
1.00
25.4
0.103
2.62
3.368
14.988
0.0166
GFRP-3
1.00
25.4
0.111
2.82
3.541
15.757
0.01694
Average
1.00
25.4
0.104
2.65
3.382
15.05
0.0162
GFRP-4
1.00
25.4
0.166
4.22
7.387
32.872
0.02195
GFRP-5
1.00
25.4
0.142
3.61
5.467
24.328
0.01699
GFRP-6
1.00
25.4
0.152
3.86
7.630
33.955
0.01868
Average
1.00
25.4
0.153
3.89
6.828
30.385
0.0192
3.8 PROPERTIES OF FRP COMPOSITES (COMPRESSION)
ACI 440.2R-08 does not allow externally bonded FRP sheets or plates to carry
compression due to the lack of testing or experimental validation. Nevertheless,
Wu (1990) reported that the compressive strength of coupons is 55% of the tensile
strength for GFRP, 78% for CFRP, and 20% for AFRP, depending on the fiber vol-
ume fraction and the resin used. Composites with fiber volume fraction of 55%-60%
are reported to have a compressive modulus equal to 80% of the tensile modulus
for GFRP, 85% for CFRP, and 100% for AFRP (Ehsani 1993). These results are
reported primarily for FRP bars, but not for sheets or plates externally bonded to
concrete using resin adhesives.
3.9 PROPERTIES OF FRP COMPOSITES (DENSITY)
Composites are known to be very lightweight materials, ranging in weight between
15%-27% of the weight of steel, as seen in Table 3.15. Accordingly, significant sav-
ings in transportation costs, dead-load reduction, and on-site ease of installation are
anticipated (ACI 440.2R-08).
3.10 PROPERTIES OF FRP COMPOSITES (THERMAL EXPANSION)
The coefficient of thermal expansion for unidirectional FRP systems varies signifi-
cantly between the fiber and the transverse directions, based on the fiber and resin
type as well as the fiber volume fraction. Typical values are listed in Table 3.16,
where concrete and steel values are also listed for reference purposes.
To determine the values of the coefficients of thermal expansion (CTE) along the
structural principal directions when the material principal directions are different
(i.e., in the case of angle plies of ±θ° between the fiber and the main structural load-
ing axis), the generalized strain-stress relationship, in the presence of temperature
changes, is invoked:
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