COMPOSITE MATERIALS

Uc5713-Jil sheth

Uc1813-Keshav sharma

What are composite materials?

• A materials system composed of two or more distinct phases whose combination produces aggregate properties different from those of its constituents

• They are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or microscopic scale within the finished structure.

Types of composite materials

• Particle-reinforced composites

• Fiber-reinforced composites

• Structural composites

• There are five basic types of composite materials: Fiber, particle, flake, laminar or layered and filled composites

Examples of composite materials

• Wood is a composite – it is made from long cellulose fibers (a polymer) held together by a much weaker substance called lignin.

• Concrete is a mix of aggregate (small stones or gravel),cement and sand.

• Fiberglass- matrix is a plastic and the reinforcement is glass.

• Nanocomposites

• Composite laminates

What are Epoxy resins?

• A family of thermosetting resins which have the following chemical group:

• When reacted with a hardener(or curing agent), they set to a hard mass which does not melt or dissolve in solvents.

• Hardeners are typically amine or anhydride based chemistry.

In what forms are Epoxies and Hardeners supplied?

• Liquids

• Solids

• Solutions

• Semi-formulated pastes

What are the advantages of Epoxies?

• Bonds strongly to most materials including metals, concrete, glass, ceramics, stone, wood, leather. Exceptions are plastics materials like polyethylene, polypropylene, Teflon, etc.

• Excellent resistance to chemicals and solvents.

• Very good electrical insulating properties.

• Outstanding mechanical strength including tensile, compressive, flexural and modulus.

• Very little shrinkage on curing, thus providing good dimensional stability.

Industries in which Epoxies are utilized

• Coatings, Paints and Lacquers.

• Civil Engineering and Construction.

• Aerospace and Industrial Composite.

• Electrical & Electronics (i.e. casting, impregnation, insulation, laminates, potting, etc).

• Adhesives and Sealants.

• Recreational and Sporting Equipment (i.e. golf shafts, skies, snowboards, tennis racquets).

• Foundries and tooling (i.e. automotive).

Coating Applications

• Civil Engineering

• Construction

• Flooring

• Industrial Maintenance

• Marine

• Powder Coatings

• Can/Coil/Packaging

• Automotive

Coatings

• Solvent-free lining of concrete and steel tanks,

• Water-based coatings for concrete.

• Powder coatings for rebars.

Mortars

• Self-leveling and trowellable floors

• Pothole repair for roads and airfields.

• Grouting of heavy machinery.

Epoxies for Civil Engineering and Construction Applications

Epoxies for Civil Engineering and Construction Applications (cont.)

Bonding

• Bonding of prefabricated elements in bridges and other structures.

• Bonding new to old concrete.

• Bonding external reinforcement to concrete.

Injection Systems

• Grouting and repair of concrete cracks.

Advantages of CompositesHigh Strength to Weight Ratio

Material Strength toWeight Ratio

Aluminum 0.8Steel 1.0Titanium alloy 1.0Glass/ Epoxy 2.86Carbon/Epoxy 3.8Aramid (Kevlar)/Epoxy 5.09

Epoxy Resins

• Diglycidyl ether of Bisphenol A

• Diglycidyl ether of Bisphenol F

• Epoxy Novolac

• Long chain aliphatic diglycidyl ethers

• Cycloaliphatic epoxy resins

• Multifunctional resins

• Brominated epoxy Resins

Epoxy Hardeners

• Aliphatic amines/ adducts

• Cycloaliphatic amines /adducts

• Polyaminoamides /Amidoamines

• Phenalkamines

• Aromatic amines

• Formulated anhydrides

• BF₃ and BCL ₃ adducts with amines

What are the limitations of Epoxies?

Limited pot life when resin and hardener are mixed.

Cured systems have poor resistance to U.V. Thus, outdoor exposure over time tends to yellow and chalk coatings and electrical insulators can begin to “track”.

Limited temperature resistance:Ambient cure: 150-250°FHeat cure: up to 360° F

Resins and Hardeners need to be handled with care in sensitive individuals to prevent dermatitis or rash.

Leading manufactures in India

• Aditya birla group

• sarafresin-india

• Epotec

• CeTePox

• CTP

References

• Civil engineering building practice Book

by  Suraj singh 004110

• Wiley online library

• IS:9162-1979. Indian standard methods of tests for epoxy resins, hardeners and epoxy resin compositions for floor topping.

• Britannica online

• Adityabirlaonline -epoxy

Thank you!