10.000
3.875
2.250
3.875
+
+
3.0 Radius Typ (4)
0.812
0.500
0.812
Figure 16. Dimensions of the coupon test specimens.
a. FRP laminate coupons after the ten-
b. Enlarged view of the failed area.
sile tests.
Figure 17. FRP laminate coupons.
further modified slightly, for manufacturing and
that the stress-strain curve is bilinear, which is
typical for most 0/90 laminates if the 90 fibers
finishing reasons. The final layup of the 12.7 mm
(0.5 in.) nominal thickness W-beam is shown in
occur at the outer layers. The change of slope from
elastic modulus E = 11.58 GPa (1.68 106 psi) to a
Figure 19.
lower value of E = 6.48 GPa (0.94 106 psi) indi-
The "wetted-out" laminate prepeg was then
cates the first ply failure of the composite. This
placed in the mold of the W-beam. A vacuum bag
transition has always occurred with a slight sound
made of polyethylene sheet was then placed
during testing. Table 3 gives the sequential test-
around the part and a vacuum created. This
ing of the laminate coupons until the most opti-
ensured against any inconsistencies in the prepeg
mum layup was developed.
layup and created a uniform homogeneous matrix.
The series of tests revealed that the layup of
After curing, each W-beam manufactured in 6.1-m
CRREL-5 laminate had the maximum strength,
(20-ft) lengths was prepared for gel coat and sub-
449.6 MPa (65,255 psi). As a result, the composite
sequently painted.
W-beam manufacturing vendor was tasked to pro-
A total of 15 guardrails, each 6.1 m (20 ft) long
duce the W-beam with this layup. The layup was
and 12.7 mm (0.5 in.) thick, was fabricated. As
16
Previous Page
