Investigations of Plastic Composite Materials
for Highway Safety Structures
PIYUSH K. DUTTA
CHAPTER 1: INTRODUCTION
This report describes the results of a study per-
crashworthiness, and safety. Each year about 5%
formed to evaluate a series of concepts using vari-
of the 36 million small sign supports on our
ous composite materials for highway safety struc-
Nation's roadsides must be replaced due to off-
tures. The structural systems for which these
the-road accidents or vandalism. Some county
materials were studied consisted of a highway
engineers spend as much as 15% of their annual
barrier W-beam guardrail, its posts and blockouts,
maintenance budgets to replace small sign sup-
sign posts, concrete reinforcing rebars, breakaway
ports. Corrosion-proof composites appear to be a
couplers, and crushable cushions for roadside
viable material for such structures. Also, the non-
sign or utility posts. The composite material sys-
conductive property of composites makes them
tems included fiber reinforced plastics (FRP) in
relatively safe during accidental contact with live
laminated and bar forms, and the commercially
power lines. Because of the lack of any large-
available recycled and reconstituted structural
volume market, the growth of production tech-
plastics.
nology for composite materials has been rather
FRP composites are a relatively new class of
slow in the U.S. The application of composites
materials and are perceived to have excellent
on high-volume roadside safety hardware items
durability. They are commercially available, and
could create a market that would support large-
their varieties range from short-glass-fiber-
scale production, lower production costs, and
reinforced thermoplastics for injection molding
make composite materials available for other
to about 70% continuous-carbon-fiber-reinforced
highway applications.
advance composites. These are the materials of
Moreover, plastics and composites hardware
choice for aircraft structural components, auto
development technology can address the crucial
body panels, appliances, and a plethora of other
national issue of recycling reclaimed plastic mate-
industrial, civil engineering construction, and
rials. This process can lead to a further reduction
consumer products (Ballinger 1991, Busel 1995,
of cost, making reinforced plastic composites an
Rizkalla and Abdelrahman 1995, Karbhari 1995,
alternative to timber and steel whenever possible.
English 1987, GangaRao 1995). Although not
In this investigation, to achieve the objective of
always as strong or rigid as metals, plastics and
evaluating the use of composite materials for road-
composites offer unique design flexibility and the
side safety hardware, literature on composites
ability to put the strength exactly where it is
design requirements, material properties, and com-
needed.
posite manufacturing processes was reviewed.
The application of plastics and composites to
A prototype guardrail (W-beam) was designed,
roadside safety hardware systems is considered
and a 91.5-m (300-ft) length of this design was
attractive for a variety of reasons, including corro-
fabricated to match or slightly overperform the
sion resistance, reduced maintenance, improved
tensile strength and stiffness of the AASHTO M180
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