Hi Karnic
As a material for a canopy manufacxtures use a 'frp'
(a fiberglass laminate, popularly often called fiberglass) rather then
fiberglass itself. Both, (frp and ABS) are a class of materials,
rather then a specific material. Both classes have a wide range of the
physical properties.
Here are the definitions and general properties:
What is what?
==============
"What is fiberglass?
Fiberglass fibers are made from molten glass extruded at a specified
diameter. The fibers are gathered into bundles and the bundles
combined create a roving. Rovings are a continuous rope, similar to
twine, and are wound on a mandrel to form a ball called a doff.
Reinforcements for frp are made from rovings that are either chopped
into short strands or woven into a cloth..."
"Frp, fiberglass reinforced plastic, is a composite made from
fiberglass reinforcement in a plastic (polymer) matrix. A construction
analogy would be the steel reinforcing bars in a concrete matrix for
highways....."
"What are plastic/polymers?
There are two basic types of plastics/polymers: thermoplastic and thermoset..."
http://www.kemlite.com/frp_encyclopedia.cfm
What is ABS = Poly(Acrylonitrile, Butadiene, Styrene)
"ABS is a copolymer of Acrylonitrile, Butadiene, and Styrene. ABS
plastics generally possess medium strength and performance and medium
cost; ABS is often used as the cost and performance dividing line
between standard plastics (PVC, polyethylene, polystyrene, etc.) and
engineering plastics (acrylic, nylon, acetal, etc.). ABS polymers can
be engineered by the manufacturer togive a range of physical
properties, depending on the ratio of the monomeric constituents and
the molecular level connectivity. Typically, a styrene-acrylonitrile
glassy phase is toughened by an amorphous
butadiene/butadiene-acrylonitrile rubber phase"
http://www.matweb.com/reference/abspolymer.asp
Laminates/composites in general:
"...the composite material is commonly referred to by the name of its
reinforcing fibers (fiberglass), an example of part-for-whole
metonymy. The plastic is most often polyester or vinylester, but other
plastics, like epoxy (GRE), are also sometimes used..."
http://en.wikipedia.org/wiki/Glass-reinforced_plastic
http://en.wikipedia.org/wiki/Composite_material
Properties:
===========
The advantage of ABS is that this material combines the strength and
rigidity of the acrylonitrile and styrene polymers with the toughness
of the polybutadiene rubber. The most amazing mechanical properties of
ABS are resistance and toughness. A variety of modifications can be
made to improve impact resistance, toughness, and heat resistance. For
instance, the impact resistance can be amplified by increasing the
proportions of polybutadiene in relation to styrene and acrylonitrile
although this causes changes in other properties. Impact resistance
does not fall off rapidly at lower temperatures
http://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene
Glass fibers are useful because of their high ratio of surface area to
weight. However, the increased surface makes them much more
susceptible to chemical attack.
By trapping air within them, blocks of glass fibre make good thermal
insulation, with a thermal resistance of 0.04 W/mK.
Glass strengths are usually tested and reported for "virgin" fibers
which have just been manufactured. The freshest, thinnest fibers are
the strongest and this is thought to be due to the fact that it is
easier for thinner fibers to bend. The more the surface is scratched,
the less the resulting tenacity is. [3] Because glass has an amorphous
structure, its properties are the same along the fiber and across the
fiber. [2] Humidity is an important factor in the tensile strength.
Moisture is easily adsorbed, and can worsen microscopic cracks and
surface defects, and lessen tenacity.
In contrast to carbon fiber, glass can undergo more elongation before
it breaks. [2]
The viscosity of the molten glass is very important for manufacturing
success. During drawing (pulling of the glass to reduce fiber
circumference) the viscosity should be relatively low. If it is too
high the fiber will break during drawing, however if it is too low the
glass will form droplets rather than drawing out into fiber.
http://en.wikipedia.org/wiki/Fiberglass
Here is a comparison made by canopy manufacturer
Canopy Materials:
" Most canopies sold in the Australian market place have either
fibreglass or ABS plastic shells. Fibreglass has a higher load bearing
strength than ABS, but ABS has higher impact strength than fibreglass.
Since it is not recommended to put any load directly onto any canopy
(see below), the greater impact strength of ABS can provide a real
benefit in the event of accident damage. In many impact situations
where fibreglass will crack or shatter, the ABS will survive
unscathed, although minor damage to both materials can be repaired.
Generally, offroad users prefer ABS canopies because they withstand
the vibration and shock of rough roads whereas fibreglass can tend to
crack in similar circumstances. The external texture of canopies is
either "leathergrain" or "smooth", depending on manufacturer's
production moulds. "Leathergrain" is more forgiving when it comes to
showing minor scuffing - it doesn't show the marks as easily..."
http://www.blueys.com.au/acc_canopies.htm
Here are data sheets on few examplw materials:
Fiberglass Reinforced Polypropylene
Super High Impact
Part Numbers: P8210; P8220; P8230
and
Polycarbonate/ABS Alloy
(FR Grade)
Part Number FA05-000FR
http://www.polymersales.com/materials-old.html
This reseller provides more specific info on many commonly used plastics
and offers informational broschures
Hedgie |