Types of Composites

TYPES OF COMPOSITES

1. Polymer composites (or) Fibre Reinforced Polymer Composites

The fibre reinforced polymer composites constitute more thart 90% (by weight) of the total composites used in various industries. The advantages of using polymer in structural composites is the ease of fabrication of complex structural shapes. It can be easily manufactured.

Preparation

Fibre-reinforced plastics are produced by suitably bonding a fibre material with a resin matrix and curing them under pressure and heat. The main reinforcing agents used in FRP composites are, glass, graphite, alumina, carbon, boron, etc. The reinforcement material can be in different forms such as short fibres, continuous filaments (or) woven fabrics.

The resin matrix commonly used in FRP are polyesters, epoxy, phenolic, silicone, and polyamide polymer resins.

Characteristics (or) Properties of FRP

1. It possess superior properties like higher yield strength, fracture strength and fatigue life.

2. Since fibre prevents slip and crack propagation, the mechanical properties of FRP gets increased.

3. It possess high corrosion resistance and heat resistance property.

The properties of FRP mainly depends on nature of the resin matrix

Resin : Reason

1. Polyester resin : To provide very good strength and mechanical properties.

2. Epoxy resin : To impart good mechanical properties.

3. Silicone resins : To impart excellent thermal and electrical properties

4. Phenolic resins : To withstand high temperatures

5. Thermoplastics (polyamide, PET, etc) : Because of its repeatability and  repairability.

T

able 4.1: Types of FRP Composites

Advantages of polymer composites (FRP)

1. Polymer composite has very high strength to weight ratio than the metal.

2. The weight of FRP is 75% lower than the weight of steel, so it improves performance, reduces energy need, simplifies handling.

3. Using polymer composite devices both capacitance and leakage current can be reduced.

4. FRP offers better corrosion resistance to a wide range of chemicals resulting in longer service life, less maintenance and repair down time.

5. FRP possesses excellent durability and fire resisting properties.

6. It is ideal for outdoor installation, because it is impervious to the effect of sunlight, heat, cold and other weather conditions.

7. Specifying the orientation of reinforcing fibres, can increase the strength and resistance to deformation of the polymer.

8. GRP (glass reinforced polymer) are strongest and most resistive to deforming forces, when the polymer fibres are parallel to the force being exerted and are weakest when the fibres are perpendicular.

9. CRP (carbon fibre reinforced polymer) in place of sheet aluminium in traditional rudded are

(i) 25% reduction in weight.

(ii) 95% reduction in components by combining parts and forming simpler moulded parts.

 

2. Metal Matrix Composites

Properties

(i) Metal matrix composites exhibit extremely good thermal stability, high strength, good stiffness and low specific weight.

(ii) MMCs also have other advantages like fracture toughness, ductility and enhanced elevated temperature performance at

(iii) They can withstand at elevated temperatures in corrosive environment than polymer composites.

Uses

(i) Polymer based composites cannot be utilized for engine parts due to their limitations in their applications at high temperatures where as MMCs are suitable alternatives with Al, Ti, Ni alloys as one of the matrix material and Al₂O₃, B, C, SiC as one of the reinforcements.

(ii) They are used in engine blades, combustion chambers, etc.

(iii) Al and Mg MMCs are used in automotive industry.

(iv) They improve fuel efficiency because of the weight reduction.

(v) Apart from aerospace, defence and automotive applications, MMCs are also used in biomedical and sports equipment industry

 

3. Ceramic Matrix Composites

Properties

1. CMCs are used at temperatures above 1500°C, because of their good corrosion resistance, stability at elevated temperatures and high compressive strength.

2. Ceramics provide necessary strength at high temperature with good oxidation resistance.

3. The matrixes used are glass, ceramics, carbides, nitrides, oxides and borides, the reinforcements are Al₂O₃, B, C, SiC and SiO₂

Uses

They are used in re-entry thermal shields in space vehicles and tiles, pump seal, round rings, brake linings etc.

 

4. Hybrid composites

Hybrid composites are new class of materials composed of a suitable polymer matrix reinforced with two different fibres (or) fillers.

Types of Hybrid composites

Functionally hybrid composites are of three types

1. Structurally hybridized composites

2. Materials hybridized in chemical bond

3. Functionally hybridized composites.

Properties

Hybrid composites possess very good properties compared to their single fibre composites.

1. They possess strong, tough and higher impact resistance.

2. When hybrid composites are stressed in tension, failure does not occur suddenly.

3. They possess balanced strength and stiffness.

4. They also have balanced thermal distortion stability, reduced weight, improved fatigue resistance.

5. They exhibit superior mechanical and tribological properties than other composites.

Uses

1. It is used in light-weight transport (land, water (or) oil) structural components.

2. It is also used in light weight orthopedic components and sporting goods.

3. It is used to make furniture like chair, table and bath tubs

4. It is used in railway coach interiors.

5. It is also used in making daily used applications like plates and spoons.

6. Automobile industry utilizes hybrid composites in many of the interior and exterior applications.