Composites
The term composites originally arose when two or more materials where combined or bonded together to form a heterogeneous mixture in order to rectify some shortcoming of a particularly useful component. Different research workers have given different definition of composites. Among this the definition given by George Lubin (1969) is that a composite material is created by the synthetic assembly of two or more components (selected filler or reinforcing agent and compatible matrix binder) in order to obtain specific characteristics and properties.
1.1 Classification of Composites
Composites can be classified on the
basis of their structural components and the matrix, according George
Lubin (1989) the composites can be classified based on the structural
components used as,
1.1.1 Thermoplastic composites
Compared to thermosetting composites, a thermoplastic composite has the following major advantages.
When applying thermosets the viscosity can be lowered, this helps in better wetting between reinforcement and matrix. One of the biggest disadvantages of thermoset composites are once it is cured it cannot be reformed into another shape.
1.2 TEXTILE STRUCTURAL REINFORCED COMPOSITES
Textile structural composites represent a class of advanced materials, which are reinforced with textile preforms for structural or load bearing applications. Presently, textile structural composites are part of a larger category of composite materials (Shishoo et al 1971 and Wiemer et al 2000). In general,composites can be defined as a selected combination of dissimilar materials with a specific internal structure and external shape. The unique combination of two material components leads to singular mechanical properties and superior performance characteristics not possible with any of the components alone.
Additionally composite materials are often overwhelmingly superior materials (e.g. metals) on strength to weight or stiffness to weight basis(Kaldenhoff and Wuifhorst 1997). Textile structure as a reinforcement and resin as matrix have led the production of textile fabric reinforced composite.
1.3 SELF REINFORCED COMPOSITE (SRC)
SRC refers to a composite comprising polymeric oriented reinforcing elements (usually fibers or tapes) or rigid particles in a matrix of the same polymer. However, there are other kinds of SRC‟s based on molecular orientation. They comprise homogeneous polymers or polymer blends that have a level of preferred molecular orientation (through extrusion, injection molding or a solid-state stretching process), where the “reinforcement” is at a molecular level. This technique has been used to develop PP-based SRCs. The preform can be developed by various techniques such as weaving, knitting, nonwoven and braiding. According to Horrocks (2004) textile preform is classified in the following manner. Figure shows the classifications of textile perform.
The term composites originally arose when two or more materials where combined or bonded together to form a heterogeneous mixture in order to rectify some shortcoming of a particularly useful component. Different research workers have given different definition of composites. Among this the definition given by George Lubin (1969) is that a composite material is created by the synthetic assembly of two or more components (selected filler or reinforcing agent and compatible matrix binder) in order to obtain specific characteristics and properties.
 |
| Textile composite |
Composite materials
have a bulk phase, which is continuous, called the matrix, and one or
more dispersed, non-continuous phases, called the reinforcement, which
usually has superior mechanical orthermal properties to the matrix. The
region between the two can be simply a surface, called an interface, or a
third phase, called an interphase.
1.1 Classification of Composites
 |
| Classification of Composites |
- Fibrous (composed of fibres in a matrix) composites
- Laminar (composed of layers of materials) composites
- Particulate (composed of layers of materials ) composites
- Flake ( flat flakes in a matrix)
- Skeletal (composed of a continuous skeletal matrix filled by Second material).
1.1.1 Thermoplastic composites
Compared to thermosetting composites, a thermoplastic composite has the following major advantages.
- Heating or steaming will not make the composites brittle.
- Shorter cure cycle and
- Ability to recycle.
- High impact strength
- Tolerance for damage is high
- Low price and recyclable.
- Thermoplastic matrix can withstand high temperatures and still possess good flow property.
1.1.2 Thermosetting composites
Composites which are produced using the thermoset matrix are named as thermoset composite. Thermoset matrix additionally requires hardener for making the composites and it also requires the curing. This will automatically increases the production cost and processing time.The degree of wetting during the production
process is important for a good adhesion between reinforcement and matrix.
Composites which are produced using the thermoset matrix are named as thermoset composite. Thermoset matrix additionally requires hardener for making the composites and it also requires the curing. This will automatically increases the production cost and processing time.The degree of wetting during the production
process is important for a good adhesion between reinforcement and matrix.
When applying thermosets the viscosity can be lowered, this helps in better wetting between reinforcement and matrix. One of the biggest disadvantages of thermoset composites are once it is cured it cannot be reformed into another shape.
1.2 TEXTILE STRUCTURAL REINFORCED COMPOSITES
Textile structural composites represent a class of advanced materials, which are reinforced with textile preforms for structural or load bearing applications. Presently, textile structural composites are part of a larger category of composite materials (Shishoo et al 1971 and Wiemer et al 2000). In general,composites can be defined as a selected combination of dissimilar materials with a specific internal structure and external shape. The unique combination of two material components leads to singular mechanical properties and superior performance characteristics not possible with any of the components alone.
Additionally composite materials are often overwhelmingly superior materials (e.g. metals) on strength to weight or stiffness to weight basis(Kaldenhoff and Wuifhorst 1997). Textile structure as a reinforcement and resin as matrix have led the production of textile fabric reinforced composite.
1.3 SELF REINFORCED COMPOSITE (SRC)
SRC refers to a composite comprising polymeric oriented reinforcing elements (usually fibers or tapes) or rigid particles in a matrix of the same polymer. However, there are other kinds of SRC‟s based on molecular orientation. They comprise homogeneous polymers or polymer blends that have a level of preferred molecular orientation (through extrusion, injection molding or a solid-state stretching process), where the “reinforcement” is at a molecular level. This technique has been used to develop PP-based SRCs. The preform can be developed by various techniques such as weaving, knitting, nonwoven and braiding. According to Horrocks (2004) textile preform is classified in the following manner. Figure shows the classifications of textile perform.
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