COMPOSITES

1. COMPOSITES GROUP: HUSTLER TONY – MATERIALS JULIAN – TERMINOLOGY & BASIC PROPERTIES HUZAIFA – FIBRES RAJINDER – COMPOSITES WITH POLYMER MATRICES ALEX & BENJI – COMPOSITES WITH METAL MATRICES

2. MATERIALS • DEFINITION: • Materials made from two or more constituent materials with significantly different physical or chemical properties. • Composite in materials engineering refers to a matrix material with fibres. • USES: • Composites have been used by people for millions of years. • It is a leading edge of materials technology that is used at • a high technology field (eg: used in a spacecraft) • PROPERTIES: • Strengths and stiffnesses of composite are much better than traditional materials. • BASIC MATRIXMATERIALS: • Metal • Glass • Polymers • Epoxy resins

3. TERMINOLOGY • Composites are generally broken into three main fields based on composition: • Polymer-matrix composites (PMC) • Metal-matrix composites (MMC) • Ceramic-matrix composites (CMC) • Other classifications are also used based on a matrix/fibre notation: • Example: Al/SiCand 6061/SiC/40p-T6 for Aluminium reinforced with Silicon Carbide • Boron and Carbon fibre reinforced polymers can use the notations BFRP and CFRP • The Reinforcement types are: • Discontinuous (Short Fibre) • Continuous Fibre • Particle – Which can be split into two categories: Dispersion Strengthened and Particle Strengthened • Dispersion strengthened is when particles between 0.01 and 0.1 microns are dispersed in a matrix that acts as the major load bearer • Particle Strengthened is when larger particles above 0.1 microns in size are added to the matrix and both the matrix and particles share the load.

4. BASIC PROPERTIES • The properties of composites are calculated through the use of the Rules of mixtures as these allow for the multiple materials in the composites and their ratios to each other. • Example: • where: • is the volume fraction of the fibres • is the material property of the fibres • is the material property of the matrix

5. FIBRES What are fibres? • Fibres are used as components in composite materials and in the manufacture of other materials. The strongest engineering materials are generally made as fibres, for example carbon fibre. What is a matrix? • The matrix is the material into which the fibre is embedded and is completely continuous. Types of fibres: • Textile fibres • Natural fibres • Synthetic fibres Function & Purpose: • The primary function of fibres in composites is to provide strength, stiffness and support to the structural load. • The purpose of the matrix is to provide shape and form, to protect the fibres from structural damage and chemical attack, to distribute stress, and to provide toughness.

6. Fibres are prepared by drawing from a molten bath, spinning or chemical vapour deposition on a substrate such as tungsten or carbon. • Heat cleaning and washing is carried out before the fibres are finally used in the fabrication of a composite. • A continuous-fibre epoxy resin tape has been introduced in the market that contains a mixture of large boron fibres and smaller-diameter carbon fibres. • While carbon is good in tension, it lacks good compressive properties. This deficiency is overcome through the use of boron fibres that exhibit their best properties in compression. • The combined material has good flexibility which help in the manufacturing of sporting goods and medical equipment. • Glass fibres cannot be used as reinforcement if the materials are to be subjected to an alkaline environment because they will be highly corroded – (use Zr2O3 glasses) • Ni-coated carbon fibre has been produced by a vapour-deposition process that provides for shielding against electromagnetic and radiofrequency interference. • This is of importance in the shielding of computer, electronic and communications equipment. • Many fibres today have started to find application as substitute materials for asbestos in ordinary commercial applications such as in the manufacture of paper, textiles, coatings, flooring, insulation and tape.

7. COMPOSITES WITH POLYMER MATRICES • Polymer-matrix composites (PMCs) have matrices of thermoplastic or thermosetting polymers - traditionally glass fibre. • Bismaleimide resins (BMIs):- same desirable properties as epoxies. hard ability, good mechanical properties, and have service temperatures of up to 250°C tougher grade and higher heat resistance. • Newly developed polyimide (PI) resins, for instance, can withstand exposure to temperatures of more than 300°C. • Polyimides- brittle and high heat resistance, difficult to ignite, less smoke, less toxic. • Polyvinyl chloride (PVC) and polystyrene – thermoplastics that are tougher and can withstand higher service temperatures. • PCT, which is a high-temperature, semi-crystalline, thermoplastic polyester that melts at 285°C and is capable of long-term service temperatures of up to 170°C

8. It is sufficiently heat resistant and is thus used in the walls of spacecraft and in fire-retarding materials in skyscrapers. • PMCs - lower weight, higher stiffness-to-weight ratio, higher fatigue-strain capability and corrosion resistance • Uses of PMCs - modern engines, transmission, shafts, couplings. • Phenolic graphite reinforced polymer composites – ued for elevated walkways, floor-support systems, racks, ladders and handrails because they can be pultruded to produce standard sections or profiles. • Glass-reinforced polymer - used for hydro cyclones, pressure vessels, pressure-vessel safety enclosures, and abrasion-resistant components. Lightweight, ultra-strong, shock-resistant

9. COMPOSITES WITH METAL MATRICES • These are materials which are fabricated by liquid-infiltration techniques such as: • High pressure infiltration casting • Squeeze casting • Vacuum infiltration casting • Compo casting • • In addition to improving strength, stiffness, abrasion resistance and reducing density, MMCs are capable of providing increased oxidation resistance at high temperatures. • • Fibrereinforcements in metal matrix materials of particular interest include: • Carbon graphite (continuous fibre) / copper • Graphite (continuous fibre) / aluminium • SiC(particulate) / magnesium

10. Properties of MMCs: • Wear resistance • Strength • Stiffness • • Applications of MMCs: • Automotive components • Brake calipers • Pump housing • Gears • Valves • Pulleys Example of a pre machined discontinuous two-dimensional ceramic-fibre preform ready for infiltration by a molten metal alloy in the manufacture of a composite connecting rod with a net-shaped metal matrix.

11. VIDEO New Carbon Composite of Nanotubes and Graphene http://www.youtube.com/watch?v=munIqrfGMZg

12. REFERENCES IOSR Journal of Engineering (IOSRJEN) ISSN: 2250-3021 Volume 2, Issue 8 (August 2012), PP 152-158 www.iosrjen.org Latest Developments in Composite Materials Lakhwinder Singh1, Geetesh Goga2, Mukesh Kumar Rathi3 1,2,3(Deptt. Of Mechanical Engineering,K.C.College of Engineering and Technology)