Today, almost any specialization for structural material can be met by combination of glass
fiber and plastic resin, which are characterized by many outstanding properties. During 1942
glass fiber reinforced composites were first used in structural aerospace parts. In the early
1960’s high strength glass fibers, S-Glass were first used in joint work between Owens corning
textile product and the united states air force later in 1968 S-2 glass began evolving into a
variety of commercial application. High strength glass fiber combine high strength, high
stability, transparency and resilience at a very reasonable cost-weight performance. The
utilities of high strength glass fiber composites are compared by physical, mechanical, electrical,
thermal, acoustical, optical and radiation properties.
Composites:
Composites are artificially produced multiphase materials having a desirable combination of the
best properties of the constituent phases or more precisely these are the materials consist of
fibers of high strength and modulus embedded in or bonded to a matrix with distinct interfaces
between them.
Structure of fiber glass
Glass describes range of material made by fusing together one or more
of the oxides of silicon, boron or phosphorus with certain oxide like
potassium, magnesium, calcium.
• Basic part of Glass fiber is Silica “SiO2”.
• In its pure form, it exists as polymer, (SiO2)n.
In the polymer it forms SiO4 groups
which are configured as a tetrahedron
with the silicon atom at the center, and
four oxygen atoms at the corners. These
atoms then form a network bonded at
the corners by sharing the oxygen atoms
Chemical Compositions
Various Properties of Different Glass Fibers:
Properties
Tensile Strength (Gpa)
Modulus (Gpa)
Elongation (%)
Density (g/cc)
Refractive Index
Coefficient of Thermal
Expansion (107/0c)
Dielectric Constant RT, 1010 Hz
E-glass
AR-glass
S-glass
3.5
73.5
4.8
2.57
1.547
3.5
175
2
2.68
1.561
4.6
86.8
5.4
2.46
-
50-52.0
6.1-6.3
75.0
-
23-27.0
5.0-5.1
Forms of the Glass Fiber Reinforcement:
Glass Fabric:
This form of glass fiber is particularly suitable for high strength, low weight laminates.
Continuous filament glass is preferred in these applications on account of it’s greater strength
and low bulk factor. The fabric woven from continuous filament yarn ranges in thickness from
0.002-0.02 inches. In general directional properties of laminates depend on the type of weave
and cloth setting employed. (We’ll discuss this later). The example of fabric-reinforced plastic is
aircraft radar. In this application, a material is required which will allow the radar rays to go
without distortion from the rays sending equipment out of the target and then back to the
radar receiving equipment on the plane. It must also stand the air pressure strain of a sonic or
supersonic speed. Combination of glass fabric and low-pressure plastic resin provides an
excellent answer to these requirements.
Combination of glass fabrics and fire-proofed polyester resin are also used for making high strength flat
and shaped laminates for aircraft components such as a ducting, panels, nose, wings tips, rudder parts,
covers, dash-boards, shelves, floors
This material is also used for hollow fishing rods, where unidirectional fabric lends itself to winding
round a solid mandrel, for body armor and for the manufacture of large article such as boats by the low
pressure technique and for many other products.
Molding Techniques:
Molding methods are almost legion. At present count more than 22 general molding methods is
basic process categories are widely used. These includes
1.Hand and spray saturating and mixing.
2.Continuous impregnation, laminating.
3.Cure or flat or corrugated panels, solid rods, hollow bar stock.
4.Compression, transfer and injection molding.
5.Filament wrapping and winding.
6.Centrifugal and static casting.
7.Rotational molding.
8.Cold forming.
9.Combination of those above.
Effect of Different Weaves:
The plain weave fabric having square setting i.e. equal number per inch of ends in the warp as
picks, is employed where uniformity in strength is desired. Another popular structure is 8-shaft
satin weave, in which each weft yarn goes under one and over seven warp yarns. It is mostly
used in heavier fabrics when lamination calls for high strength in all direction and where a
smooth surface and decorative appearance are desired. Due to lower crimp or ‘weaving take
up’ the strength of a satin weave fabric is comparatively greater then of a plain weave fabric.
When maximum strength in one direction is required at a maximum weight, a unidirectional
weave is employed. In order to produce such a fabric, usually a large amount of relatively
strong warp yarn and fewer weaker weft yarns are employed.
Non-woven materials from glass fibre are dominated because least labour intensive and most
efficient to manufacture.
Figure 1 Different weaves of glass fiber
Properties of fiberglass:
Mechanical strength: Fiberglass has a specific resistance greater than steel. So, it is used to
make high-performance
Electrical characteristics: Fiberglass is a good electrical insulator even at low thickness.
Incombustibility: Since fiberglass is a mineral material, it is naturally incombustible. It does
not propagate or support a flame. It does not emit smoke or toxic products when exposed to
heat.
Dimensional stability: Fiberglass is not sensitive to variations in temperature and
hygrometry. It has a low coefficient of linear expansion.
Compatibility with organic matrices: Fiberglass can have varying sizes and has the ability
to combine with many synthetic resins and certain mineral matrices like cement.
Non-rotting: Fiberglass does not rot and remains unaffected by the action of rodents and
insects.
Thermal conductivity: Fiberglass has low thermal conductivity making it highly useful in the
building industry.
Dielectric permeability: This property of fiberglass makes it suitable for electromagnetic
windows.
Types and forms of fiberglass:
Depending on the raw materials used and their proportions to make fiberglass, fiberglass can be
classified into following major types:
A-glass: A glass is also called as alkali glass and is resistant to chemicals. Due to the composition of A
glass fiber, it is close to window glass. In some parts of the world, it is used to make process equipment.
C-glass: C-glass offers very good resistance to chemical impact and is also called as chemical glass.
E-glass: It is also called as electrical glass and is a very good insulator of electricity.
AE-glass: This is alkali resistant glass.
S glass: It is also called as structural glass and is known for its mechanical properties.
Fiberglass comes in various forms to suite various applications, the major ones being:
Fiberglass Tape: Fiberglass tapes are made up of glass fiber yarns and are known for their thermal
insulation properties. This form of fiberglass finds wide applications in wrapping vessels, hot pipelines,
and the likes.
Fiberglass Cloth: Fiberglass cloth is smooth and is available in various variants like glass fiber yarns and
glass filament yarns. It is widely used as heat shields, in fire curtains and others.
Fiberglass Rope: Ropes are braided from glass fiber yarns and are used for packing purposes.
Properties of fiberglass