10
1
5 Energy Requirement—The type of processing technology
adopted for the fabrication of composites is the first
requirement. For example, optimum heating and least
post-fabrication operations reduce the energy requirements
of the fabrication of the product. Energy saving also is
linked with product design, selection of raw materials,
process selection, and post- fabrication operations.
5 Cost-Effectiveness—The selection of raw materials and maintaining the processing parameters make the composite product
cost-effective. For example, a storage container may be made
out of hand with a layup process using a split cavity mould and
glass fibre-reinforced polyester resin. Another way is to make it
using a filament winding process with a glass fibre-reinforced
epoxy resin. The latter will cost more, whereas the first process
will create the product for its intended use at comparatively
extremely low cost.
1.4 Classification
Polymer-based composite materials are generally classified on the
basis of the geometry of a representative unit of reinforcement. The
reinforcement may be in the form of fibres or particles. Particulatefilled composites consist of a continuous matrix phase, while the
discontinuous filler phase is made up of distinct particles. Fillers are
finely divided solids that are originally introduced into polymers to
lower the cost and to increase stiffness and hardness. Fibre-filled
composites consist of a two-dimensional distribution of randomly
oriented chopped fibres as the discontinuous phase (e.g. glass fibrefilled composites).
Generally, composites having a fibre length < 15 mm are called
short fibres, and reinforced composites and composites having a
fibre length > 15 mm are called long or continuous fibre-reinforced
composites. The short fibres having aspect ratio (length/diameter)
>100 are classified as reinforcing fibres [11]. A detailed classification
of polymeric composites is given in . Fig. 1.4.
? Example 1.3 At what aspect ratio will short glass
fibre-reinforced epoxy composites attain the maximum tensile
strength?
v Answer
In a well-aligned short fibre-reinforced epoxy composite, the
strength of the composite will reach the maximum at 10l c (l c is
the critical length of the fibre). An l c of glass fibre is
approximately 1.5 mm. Therefore, a 15 mm length of reinforcing
glass fibre would be required to achieve maximum properties
of the composite. 4l c will yield up to 90% of the maximum
composite strength.
Apart from previous classification, composites are classified based
on the matrix material used in them.
Chapter 1 · Introduction
1
5 Energy Requirement—The type of processing technology
adopted for the fabrication of composites is the first
requirement. For example, optimum heating and least
post-fabrication operations reduce the energy requirements
of the fabrication of the product. Energy saving also is
linked with product design, selection of raw materials,
process selection, and post- fabrication operations.
5 Cost-Effectiveness—The selection of raw materials and maintaining the processing parameters make the composite product
cost-effective. For example, a storage container may be made
out of hand with a layup process using a split cavity mould and
glass fibre-reinforced polyester resin. Another way is to make it
using a filament winding process with a glass fibre-reinforced
epoxy resin. The latter will cost more, whereas the first process
will create the product for its intended use at comparatively
extremely low cost.
1.4 Classification
Polymer-based composite materials are generally classified on the
basis of the geometry of a representative unit of reinforcement. The
reinforcement may be in the form of fibres or particles. Particulatefilled composites consist of a continuous matrix phase, while the
discontinuous filler phase is made up of distinct particles. Fillers are
finely divided solids that are originally introduced into polymers to
lower the cost and to increase stiffness and hardness. Fibre-filled
composites consist of a two-dimensional distribution of randomly
oriented chopped fibres as the discontinuous phase (e.g. glass fibrefilled composites).
Generally, composites having a fibre length < 15 mm are called
short fibres, and reinforced composites and composites having a
fibre length > 15 mm are called long or continuous fibre-reinforced
composites. The short fibres having aspect ratio (length/diameter)
>100 are classified as reinforcing fibres [11]. A detailed classification
of polymeric composites is given in . Fig. 1.4.
? Example 1.3 At what aspect ratio will short glass
fibre-reinforced epoxy composites attain the maximum tensile
strength?
v Answer
In a well-aligned short fibre-reinforced epoxy composite, the
strength of the composite will reach the maximum at 10l c (l c is
the critical length of the fibre). An l c of glass fibre is
approximately 1.5 mm. Therefore, a 15 mm length of reinforcing
glass fibre would be required to achieve maximum properties
of the composite. 4l c will yield up to 90% of the maximum
composite strength.
Apart from previous classification, composites are classified based
on the matrix material used in them.
Chapter 1 · Introduction