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A report on

composite materials

Submitted to:- mr. Amardeep kumar

submitted by:- Jabi khan(k12251) Vasim khan gori ( k12519)

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Contents

• Introduction• Examples• Types • Applications• Summary

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A Composite material is a material system composed of two or more macro constituents that differ in shape and chemical composition and which are insoluble in each other. The history of composite materials dates back to early 20th century. In 1940, fiber glass was first used to reinforce epoxy.

INTRODUCTION

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ExamplesComposites can be found in:

-Boat hulls-The aerospace industry (structural components as well as engines

and motors)-Automotive parts (panels, frames, dashboards, body repairs)

-Sinks, bathtubs, hot tubs, swimming pools-Cement buildings, bridges

-Surfboards, snowboards, skis-Golf clubs, fishing poles, hockey sticks

-Trees are technically composite materials, plywood-Electrical boxes, circuit boards, contacts

-Everywhere

Career Point CaresMECH 473 ~ LECTURE 15: COMPOSITES

TYPES

Composites can be classified by their matrix material which include:

-Metal matrix composites (MMC’s)

-Ceramic matrix composites (CMC’s)

-Polymer matrix composites (PMC’s) or sometimes referred to as organic matrix composites (OMC’s)

Career Point CaresMECH 473 ~ LECTURE 15: COMPOSITES

1. MMC - Metal Matrix Composites-The matrix is relatively soft and flexible.

-The reinforcement must have high strength and stiffness-Since the load must be transferred from the matrix to the

reinforcement, the reinforcement-matrix bond must be strong.

MMC use:-Two types of particulates ( dispersion strengthened alloys and regular

particulate composites)-Or long fiber reinforcements

Career Point CaresMECH 473 ~ LECTURE 15: COMPOSITES

2. PMC - Polymer Matrix Composites-The matrix is relatively soft and flexible-The reinforcement must have high strength and stiffness-Since the load must be transferred from matrix to reinforcement, the reinforcement-matrix bond must be strong

3. CMC – Ceramic Matrix Composites-The matrix is relatively hard and brittle-The reinforcement must have high tensile strength to arrest crack growth-The reinforcement must be free to pull out as a crack extends, so the reinforcement-matrix bond must be relatively weak

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• Composites: -- Multiphase material w/significant proportions of each phase.

• Dispersed phase: -- Purpose: enhance matrix properties. MMC: increase sy, TS, creep resist. CMC: increase Kc PMC: increase E, sy, TS, creep resist. -- Classification: Particle, fiber, structural

• Matrix: -- The continuous phase -- Purpose is to: - transfer stress to other phases - protect phases from environment -- Classification: MMC, CMC, PMC

metal ceramic polymer

Terminology/Classification

woven fibers

cross section view

0.5 mm

0.5 mm

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• Filament Winding– Ex: pressure tanks– Continuous filaments wound onto mandrel

Adapted from Fig. 16.15, Callister 7e. [Fig. 16.15 is from N. L. Hancox, (Editor), Fibre Composite Hybrid Materials, The Macmillan Company, New York, 1981.]

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Filament Winding Characteristics۰Because of the tension, reentrant shapes cannot be produced.

۰CNC winding machines with several degrees of freedom (sometimes 7) are frequently employed.

۰The filament (or tape, tow, or band) is either precoated with the polymer or is drawn through a polymer bath so that it picks up polymer on its way to the winder.

۰Void volume can be higher (3%)

۰The cost is about half that of tape laying

۰Productivity is high (50 kg/h).

۰Applications include: fabrication of composite pipes, tanks, and pressure vessels. Carbon fiber reinforced rocket motor cases used for Space Shuttle and other rockets are made this way.

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MANUFACTURING OF POLYMER-MATRIX COMPOSITES

-The method of manufacturing composites is very important to the design and outcome of the product-With traditional materials one starts out with a blank piece of material ie: rod, ingot, sheet, etc and works it to produce the desired part. -However, this is not the case with polymer-matrix composites.-With these composites the material and the component are being produced at the same time, therefore we aim for the product to be a net or near net shape with little to no post processing

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Hand Lay-Up/Spray-Up

-Oldest and most commonly used manufacturing method -Usually used to produce polyester or epoxy resin parts such as boat hulls, tanks and

vessels, pick-up truck canopies-The method is quite simple, the resin and reinforcement is placed against the surface

of an open (one sided) mold and allowed to cure or in the case of spray-up the resin/reinforcement is sprayed onto the mold with a spray gun

-Often a gel coat is applied to the mold prior to produce a better surface quality and protect the composite from the elements-A gel coat is a resin usually 0.4 to 0.7 mm thick, commonly seen on the outer surface of smaller boats

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Hand Lay-Up/Spray-Up-The pros of this process include: low initial start up cost, easy to change mold/design, on-site production possible (ie portable process) -The cons include: labor intensive, the quality of parts depends on operator’s skill and therefore inconsistent, only one good side to the part

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Prepreg

-A pregreg (short for preimpregnated) is a composite that comes with the resin already added to the reinforcement

-This means that the only concern when working with prepreg is shaping the part

-Since the resin is already mixed (resin and catalyst) there is a limited shelf life

-For the same reason prepreg must be cured in an oven or autoclave

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-Prepreg can be used in a few different ways-It can be placed against a mold similar to the hand lay-up method-Once placed in the mold the material must be compressed and cured according to a specific pressure/temperature cycle-This is often done by means of a vacuum bag where a thin plastic cover is secured overtop of the composite and the air is vacuumed out -This process can reduce manufacturing time and produce a stronger part-Another process used is ‘automated tape lay-up’-This process uses a large automated roller similar to a packing tape roller -The roller applies the tape with pressure which eliminates the need for a vacuum bag- Automated tape lay-up is used to produce large parts, generally in aerospace applications and is also capable of 3-d parts

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-Similar to extrusion of metal parts -Pultrusion involves pulling resin-impregnated glass strands through a die

-Standard extruded shapes can easily be produced such as pipes, channels, I-beams, etc.

Pultrusion

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Pultrusion

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• Composites are classified according to: -- the matrix material (CMC, MMC, PMC) -- the reinforcement geometry (particles, fibers, layers).• Composites enhance matrix properties: -- MMC: enhance sy, TS, creep performance -- CMC: enhance Kc -- PMC: enhance E, sy, TS, creep performance• Particulate-reinforced: -- Elastic modulus can be estimated. -- Properties are isotropic.• Fiber-reinforced: -- Elastic modulus and TS can be estimated along fiber dir. -- Properties can be isotropic or anisotropic.• Structural: -- Based on build-up of sandwiches in layered form.

Summary

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