CHAPTER 8: GENERAL REMARKS AND RECOMMENDATIONS
Composites are not being used in any large
linear shape after the load was removed. Thus, in
scale for highway safety structures. Yet, over the
installations of FRP W-beam, the post-damage re-
decade from 19841993, composites production
placements could perhaps be delayed. Another
grew about 40% in the U.S., from 0.79 to 1.11 mil-
major difference with steel is in the energy absorp-
lion Mg (0.87 to 1.22 million tons) (Phelps 1994).
tion characteristics. The drop impact tests showed
This growth, although slow, happened only be-
that the fracture initiation energy of the FRP is
cause of many significant advantages of compos-
higher than steel's, because FRP's brittle behav-
ites in civil engineering applications over tradi-
ior in post-fracture energy absorption is lower.
tional materials. The present studies have shown
However, for composites, the properties of fibers
how composites could be incorporated into com-
and resins and the geometrical arrangement of the
ponents of highway safety structures. The defi-
fibers can be controlled so that progressive crush-
nition of composites in this case included both
ing occurs.
the fiber-reinforced plastics (FRP) and the com-
The study showed that it is feasible to produce
posites of recycled plastics with other fibrous ad-
a W-beam of the same profile but of a different
ditives like sawdust. The safety structures for
thickness than the standard AASHTO steel W-
which composites were considered included W-
beams. The laminate designs could be custom-
beam guardrails, guardrail posts and blockouts,
ized and optimized to obtain the desired strength,
rebars for concrete reinforcement, breakaway cou-
stiffness, and impact characteristics. However, the
plers for the luminaries and sign supports, and
splicing and jointing techniques are yet to be
crushable cushions for roadside fixed objects like
developed. In the standard 19.05-mm (0.75-in.)
poles and trees.
bolt pullout tests, the joint failed at only about
The design study of FRP composite W-beam
14% of the laminate strength. This is an area of
guardrail was limited to a small batch fabrication
future research.
process, such as hand layup with vacuum bag
In this effort, we tried to mimic the shape of
technology. The scope did not allow developing
the steel W-beam and then look at the perfor-
commercial fabrication technology like tooling
mance. In a wider scope of research, a more desir-
and dies for pultrusion processes. However, the
able goal would possibly be to reinvestigate what
batches were made in sufficient quantities and in
mechanical performance and functional goals are
three different thickness to test them for compara-
needed for a guardrail, and then review whether
tive mechanical performance.
the current W-beam profile is also ideal for com-
The designing and manufacturing of the FRP
posite guardrails. In future studies, different pro-
W-beam profile showed that the process is more
files may emerge that would have better failure
an art than a science. The vendor used the lami-
characteristics and, consequently, better energy
nate theory as a first approximation to produce
management in overall structure and interaction
the first batch (RL) of laminates, but the desired
with posts and blockouts.
tensile strength of 482.3 MPa (70,000 psi) was not
The study of the applications of composites for
developed. Subsequently, a series of batches was
posts and blockouts focused totally on recycled
produced through trial and error (see Table 3),
plastic composites (RPC). This was an attractive
where the knowledge and experience of the ven-
goal from the perspective of improving the envi-
dor contributed to achieving the final and opti-
ronment by first developing an increased oppor-
mum strength of 447.9 MPa (65,000 psi). The
tunity for the use of plastic wastes, and then re-
vacuum process did not lead to sufficient squeez-
ducing timber consumption and the associated
ing pressure for improving the fiber volume frac-
groundwater contamination from timber preser-
tion, as did the pultrusion process. The pultrusion
vatives as creosote. The commercially available
process also produced a higher tensile strength.
RPC materials were examined and a selected RPC
The stiffness of the 6.1-m- (20-ft-) long FRP
was thoroughly tested for mechanical properties.
W-beams was sufficient for transportation and
No standard test methods were available for these
handling purposes, but was about one-third of
materials, and the compression, tension, and flex-
steel W-beam's stiffness (see Table 5). This may
ural test methods needed to be developed. The
not be a major disadvantage in its application as a
results of the compression tests, in which rela-
guardrail. In flexural tests, it was observed that
tively larger sized specimens were used, showed
even a fractured FRP W-beam bounced back to a
much less variability than the tension and flex
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