Final Work

NATIONAL UNIVERSITY OF SCIENCES &

TECHNOLOGY

Final Year Project ReportTitle: Design and make a Vacuum Bagging System For Composite laboratory for preparing a multi-ply fabric reinforced composite material flat panels

Project Members Name: AasimIftikharRegn. No. ME-732-07

Name: M.NoumanAbidRegn. No. ME-737-07

Name: UrfaRasool

Regn .No. ME-747-07

Advisor Name: Dr. Johar K. FarooqiDesignation: Associate Professor

Examiner Name: Dr.S A HassanDesignation: Professor

Co-Examiner Name: Mr.Saeed AhmedDesignation: Lecturer

PAKISTAN NAVY ENGINEERING COLLEGEDepartment of Engineering Sciences

23rd December 2010

TABLE OF CONTENTS

A List of Tables iB List of Figures iC List of Graphs iD Abstract iiE Scope iiiF Project Plan iv

1 INTRODUCTION1.1 Fiber Reinforced Composites1.2 Methods to Produce Fiber Reinforced Composites1.2.1 Hand Lay-Up1.2.2 Spray Lay-up1.2.3 Auto Claves1.2.4 Resin transfer molding1.2.5 Vacuum Bagging1.3 Advantages And Disadvantages Of Vacuum Bagging1.4 How Vacuum Bagging Systems Work??

2 VACUUM BAGGING2.1 Theory2.2 Vacuum Bagging Equipment2.2.1 Vacuum Pump2.2.2 Vacuum Bagging Materials2.2.3 Plumbing System2.2.4 Vacuum Bagging Molds3 CONCEPT EVALUATION3.1 Basic Theme For design Selection3.1.1 Design Concept 13.1.2 Design Concept 23.2 Weighting and Rating Matrix3.2.1 Weighting Matrix3.2.2 Rating Matrix

4 FIBERS REINFORCEMENT4.1 Difference between Polyester and Epoxy Resins4.1.1 Resin Comparison Summary4.2 Weighting and Rating Matrix

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4.2.1 Weighting Matrix4.2.2 Rating Matrix4.3 Reinforcements4.3.1 Type Of Reinforcements4.3.2 Type Of Fibers By Orientation4.4 Weighting and rating Matrix For Carbon Fiber and Glass fiber4.4.1 Weighting Matrix 4.4.2 Rating Matrix

5 COMPONENTS USED IN PROJECT5.1 Fabrics And Films5.2 Reinforcements and Chemicals5.3 Mechanical Components5.4 Cost Analysis

6 FABRICATION DETAIL6.1 Plumbing System6.2 Fabrics, Films And Moulds6.3 Assembling of vacuum bagging system6.4 Chemicals and resins

7 CALCULATIONS7.1 Calculating laminating resins7.2 Calculating Gel coat and resins7.3 Calculating FVF7.4 Calculating CPT7.5 Calculating density of fiber reinforced material7.6 Rules of mixture7.7 Calculating ply-longitudinal tensile modulus7.8 Calculating ply-transverse tensile modulus7.9 Calculating coefficient of longitudinal thermal expansion7.10 Calculating coefficient of transverse thermal expansion7.11 Calculating poison ratio8 STANDARD OPERATING PROCEDURES9 SAFETY MEASURES, RISK ASSESSMENT AND RECOMMENDATIONS9.1 Safety Measures9.2 Project Risk Assessment9.3 Future Recommendations

Appendices

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Appendix A SYSTEM OF REQUIREMENTS 48Appendix B GANTT CHART 51Appendix C SPECIFICATIONS OF FIBER GLASS FABRICS 53Appendix C2 MECHANICAL PROPERTIES OF E-GLASS FIBERS 54Appendix C3 MECHANICAL PROPERTIES OF POLYESTER RESINAppendix D DESIGN DRAFT 55Appendix F REFERENCES AND RESOURCES 56

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LIST OF TABLES Table 4.1 Advantages and Disadvantages of Polyester and EpoxyTable 7.1 Calculations

LIST OF FIGURES

Fig 1.1 A Schematic of Hand LayupFig 1.2 A Schematic of Spray Layup Fig 1.3 An autoclaveFig 1.4 A Schematic of Resin Transfer moldingFig 1.5 A Schematic of Vacuum Bagging SystemFig 1.6 A typical vacuum bagging system Lay upFig 2.1 Vacuum Bagging EquipmentFig 2.2 Schematic of Materials in Vacuum BaggingFig 4.1 Idealized Chemical Structure of a Typical Isophthalic PolyesterFig 4.2 Schematic Representation Polyester Resin (Uncured)Fig 4.3 Schematic Representation Of Polyester Resin (Cured)Fig 6.1 Vacuum Pump Fig 6.2 Vacuum GaugeFig 6.3 Vacuum HoseFig 6.4 Ball Valve Fig 6.5 Vacuum Throttle ValveFig 6.6 Resin TrapFig 6.7 Vacuum FittingFig 6.8 Plumbing systemFig 7.1 Fiber (longitudinal) and transverse directionFig 7.2 Tensile modulus in longitudinal and transverse directionFig 8.1 Application Of Gel Coat On MoldFig 8.2 Application Of Releasing Agent On MoldFig 8.3 Placement Of Fiberglass reinforcement In MoldFig 8.4 Placing release fabricFig 8.5 Placing breather material over Release fabricFig 8.6 Placing Perforated filmFig 8.7 Connecting vacuum line with Vacuum BagFig 8.8 Removing Fabrics and Vacuum Bag from laminateFig 8.9 Cured laminate Of Chopped Strand Mat

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ACKNOWLEDGEMENT1. We want to express our sincere gratitude to Dr Johar K Farooqi who provided us the opportunity to work on vacuum bagging system. As our project adviser he led us all the way from the front and gave us much of his precious time out of his hectic schedules. His timely guidance and experience was a continuous source of inspiration throughout our project work.2. We are also thankful to assistant professor Dr S A Hassan and Mr. Saeed Ahmed who provided us invaluable critique on this project and also useful references which were of extreme help and without whom we consider our work to be incomplete.

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ABSTRACT

The vacuum bagging system is a manufacturing process that is being used at various levels in the developed countries for making different composite products. In Pakistan some companies are using this technique in the defense oriented projects for the advancement in the modern system. Considering its scope, it was realized to establish a basic framework for vacuum bagging system for the processing of composite material at PNEC. Hence a project to develop the vacuum bagging system in the Composite lab was assigned as final year project.

Vacuum bagging is a technique employed to create mechanical pressure on a laminate during its cure cycle. Pressurizing a composite lamination serves several functions. Firstly it removes trapped air between layers; these trapped air bubbles are basically the source of cracks and failure of the product. So by removing the air bubbles from the laminate, means the increase in the strength and life of the product. Secondly, compaction of the fiber layers for efficient force transmission among fiber bundles and prevents shifting of fiber orientation during cure. Thirdly, it minimizes humidity. Finally, and most importantly, the vacuum bagging technique optimizes the fiber-to-resin ratio in the composite part.

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SCOPEThe final year projects emphasizes of following points

Design and fabrication of vacuum bagging system for making multi-ply fabric reinforced composite flat panels.

The system is designed as per the environment of Karachi but can be used in similar climate conditions.

Locally available components and material should be utilized. The device has low installation cost and less maintenance is required. The device should be user friendly. The device must also be environment friendly as proper safety measures should

be adopted. The device will be design in such a way that it will fit in composite material lab

and will replace hand lay up process that is being used right now in the lab.

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PROJECT PLANIn order to meet the project goals, it was important that each major aspect of the project was identified and planned in order to allocate sufficient resources and monitor progress. This was achieved through the generation of a Gantt chart. It was structured around main deadline dates, divided into logical and workable phases. The same has been attached in Appendix ‘A’.

Each member of the project team had taken responsibility for the timely completion of various tasks listed in the project.

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CHAPTER 1: INTRODUCTION

1.1 INTRODUCTION TO FIBER REINFORCED COMPOSITE MATERIALS:

Composite materials consist of two or more materials which together produce desirable properties that cannot be achieved with any of the constituents alone. Fiber-reinforced composite materials, for example, contain high strength and high modulus fibers in a matrix material. Reinforced steel bars embedded in concrete provide an example of fiber-reinforced composites. In these composites, fibers are the principal load-carrying members, and the matrix material keeps the fibers together, acts as a load-transfer medium between fibers, and protects fibers from being exposed to the environment (e.g.moisture,humidity,etc)

Fiber-reinforced composite materials for structural applications are often made in the form of a thin layer, called lamina. A lamina is a macro unit of material whose material properties are determined through appropriate laboratory tests. Structural elements, such as bars, beams or plates are then formed by stacking the layers to achieve desired strength and stiffness. Fiber orientation in each lamina and stacking sequence of the layers can be chosen to achieve desired strength and stiffness for a specific application.

1.2 METHODS OF PRODUCING FIBER REINFORCED COMPOSITES:

1) HAND LAY UP2) SPRAY TECHNIQUES3) AUTOCLAVES4) RESIN TRANSFER MOLDING (RTM)5) VACUUM BAGGING

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1.2.1 HAND LAY UP:

Hand layup is the simplest method for manufacturing fiber reinforced composite flat panels. It is usually applied for large components but does have a demerit of labor extensive method. Glass roving or woven fabric etc is positioned manually in open mould and resin is mixed either by 1) pouring, 2) brushing or spraying into the glass fiber reinforcement. Air which is trapped inside the composite is removed manually by the means of squeegees and rollers. Thermosetting resins such as polyester and epoxy are mostly used as the matrix resins. By adding catalyst in the resin system curing is started, which helps in hardening the composite structure without the help of external heat. Pigmented gel coat is used for a high quality flat panel

Fig 1.1 Schematic for Hand Lay up Process [From www.composites.ugent.be]

1.2.2 SPRAY-UP TECHNIQUE:The spray-up technique is less labor intensive than the hand lay-up method. It involves the simultaneous deposition of chopped glass fiber roving and polymer onto the mould with a spray gun. The roving is fed through a chopping unit and projected into the resin stream. The glass resin mixture is then rolled by a split washer roller to remove any air.After the initial polymerization of the composite, and when it has been remolded, the unit must be cured usually by heating for eight hours a 60°C.

As the tooling costs for the above two processes are low, the designer has considerable versatility from the point of view of shape and form.

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Fig 1.2 Schematic for Spray-LAYUP technique[From www.ale.nl/index.php?cid=72]

1.2.3 AUTOCLAVES:

Autoclaves are used when maximum fiber/resin content is required in order to both elevate the temperature and pressure around the mould while curing the high performance parts. The biggest disadvantage with autoclave is that they are expensive then most of the other equipments and are not readily available

A process using a two-sided mould set that forms both surfaces of the panel. On the lower side is a rigid mold and on the upper side is a flexible membrane made from silicone. The assembly is placed into an autoclave. This process is generally performed at both elevated pressure and elevated temperature. An autoclave can elevate the pressure on a laminate two to three atmospheres

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Fig 1.3An Autoclave Used for Producing Composites

1.2.4RESIN TRANSFER MOULDING:

Resin Transfer Molding is a closed molding process used for moderate volume of productions. CSM (Chopped Strand Mat) and woven reinforcement is laid up dry in the bottom mold half. For complex mould shapes preformed glass fiber reinforcements are used. Closed mould is used and a low viscosity resin which is pre-catalyzed is poured in, while the located vents help in displacing the air. Metered mixing equipment controls resin-catalyst ratios that are mixed through a motionless/static mixer and injected into the mold port. Polyester, epoxy, and phenolics are commonly used matrix resins. Advantages of RTM of uniform thickness, and low emissions makes it preferable over contact molding methods. Gel coat is applied to the mold surface before the molding process to get the optimized surface finish.

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Fig 1.4 Schematic for Resin Transfer Molding[FROM www.aoc-resins.com]

1.2.5 VACUUM BAGGING:

Vacuum bagging system uses a technique by which the vacuum is created. Upon sealing the VBS (Vacuum Bagging System) ,air pressure between both sides of air tight barrier and atmospheric pressure is equal. By using the vacuum pump air is removed from the closed system, vacuum bag is compressed to the inside reducing the inside bag pressure while the pressure outside atmosphere is constant at 14.7 psi or approximately 30"Hg.pressure differential exists between the closed system(inside VBS) and open atmosphere which is responsible for providing the enough uniform clamping mechanical force.

Fig 1.5Schematic for Vacuum Bagging[From www.bertram31.com]

1.3 ADVANTAGES:

Uniform layup. Product contains higher glass to resin ratio. Strength to weight ratio is better. By using VBS laminates with higher fiber content can be produced instead of

using standard wet lay-up techniques.

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VBS provides us with lower void contents than wet lay-up.

Health and safety: Amount of volatiles emitted is less when the VBS system is used

The big advantage of vacuum bagging is in the simplicity and variety of the molds used. The atmosphere is not only pushing down on the top of the envelope, but it is also pushing up equally on the bottom of the envelope or mold. Since atmospheric pressure provides equal and even clamping pressure to the back of the mold, the mold only has to be strong enough to hold the laminate in its desired shape until the epoxy has cured. Therefore, most molds can be relatively light weight and easy to build.

Vacuum bagging also gives us the means to control excess adhesive in the laminate, resulting in higher fiber-to-resin ratios. This translates into higher strength-to-weight ratios and cost advantages for the builder.

Disadvantages of vacuum Bagginga)Costly process:The extra process adds cost both in labor and in disposable bagging materials.

b)High level skills required:Higher level of skill is required by the operators.

c)Low productivity:Vacuum Bagging low production rates due to bagging stage.

1.4 HOW VACUUM BAGGING SYSTEM WORKS?Vacuum bagging system uses a technique by which the vacuum is created, which acts as a barrier(air tight) between atmosphere and enclosed system. Upon sealing the VBS (Vacuum Bagging System),air pressure between both sides of air tight barrier and atmospheric pressure is equal. By using the vacuum pump air is removed from the closed system, vacuum bag is compressed to the inside reducing the inside bag pressure while the pressure outside atmosphere is constant at 14.7 PSI or approximately 30"Hg.There exist a pressure differential between closed system(inside VBS) and open atmosphere which is responsible for providing the enough uniform clamping mechanical force.

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Fig 1.6 Typical vacuum bagging lay-up[From West System}

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CHAPTER 2: VACUUM BAGGING SYSTEM

2.1 THEORY:

The composites are used increasingly due to the strength-to-weight advantages that they offer while keeping in mind they provide us the optimized fiber resin ratio. The reinforcements (carbon and glass fiber etc) that are used in composites are not strong enough, so they can’t be used in their textile state. While on the other hand we mostly use thermosetting resins polyester and epoxy which are brittle in nature if they are cured without reinforcement. Also it is taken into consideration that resin is not in excess amount which will mean that laminate has properties of resin only while if its amount is less laminate will contain dry spots where the reinforcement is left dry. For optimizing its content, we try to make whole reinforcement saturated with resin in little excess so we get the desired composite properties. The vacuum bagging system uses the method of "squeezing out" excess quantity of resin so that the optimum amount of fiber-resin ratio is obtained.

Atmospheric pressure is mainly used in vacuum bagging system to provide the force (clamping) to hold the laminated plies. Laminate is inside an airtight and sealed envelope. Pressure on outside and inside envelope is equal to atmospheric pressure. Vacuum pump evacuates air from the envelope, reducing pressure inside the envelope, while no change in outside air pressure of the envelope. It is this pressure which causes the equal and even pressure all over the envelope surface. Clamping force is determined by amount of pressure differential acting between the inside and outside of surfaces of the envelope. The maximum pressure which can act upon the composite is one atmosphere[1 atm]. While the realistic amount of pressure differential will be 12-25 inches of mercury.

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2.2 VACUUM BAGGING EQUIPMENT:

Fig 2.1 Vacuum Bagging Equipment And Components[From West System]

2.2.1 VACUUM PUMP:

Vacuum Pump is the main component of a VBS .Vacuum pumps perform the same mechanical operations like air compressors, but their working is different to compressors, air is drawn out of the closed system and exhausted to atmosphere. Vacuum pumps are specified by:

1) vacuum pressure or “Hg maximum”2) their displacement in cubic feet per minute (CFM)3) the horsepower required to drive the pump

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1)VACUUM PRESSURE

Vacuum Pressure or Hg maximum is the maximum limit of vacuum level recommended for a specific vacuum pump. It’s measured in inches of Mercury or Hg. Vacuum level refers to the maximum amount of clamping pressure that can be generated on a vacuum system.

2)HORSE POWER AND PERFORMANCE:Horse power requirement of pump is the measure of efficiency of pump and doesn’t tellAbout the suitability of vacuum pump for the vacuum bagging. When we are selecting a pump,” “Hg maximum” and “CFM ratings“are taken into consideration rather than horsepower.

Fig 2.2 Graph between Vacuum level and displacement

3)DISPLACEMENT:CFM or the air volume that can be moved by a pump in also important criteria while selecting a vacuum pump. But creating a perfectly airtight VBS is an ideal concept and is not possible in real world as there would be leaks in the system allowing air to pass through. If the vacuum bagging system (VBS) was absolutely airtight that is no air can pass through the VBS, pump of any power rating would be able to pull off the maximum

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amount of vacuum pressure regardless of the size of the system. Increasing the CFM rating means that pump can reach closer to its maximum capacity

VACUUM PUMP SELECTION:

Minimum pump requirements are determined by the size of mold and quantity of material which is laminated. We are laminating flat panels which consist of a few layers of glass fibers for which, 5” or 6” Hg (2.5-3 psi) vacuum pressure will provide enough pressure for a good bond between all of the layers. Area of the panel of a few square feet requires a 1 or 2 CFM pump which will be enough to maintain the desired level of pressure. The panel area is directly proportional to the CFM requirement A displacement of 3.5 CFM may be adequate for up to a 14’ panel. Poor seals in the plumbing system or envelope, or material which allows air leakage, will require a larger capacity pump to maintain satisfactory vacuum pressure. Smaller pump is required if system is enough airtight.

PUMP TYPES: Vacuum pump types according to construction include:1) Piston pump2) Rotary vane pump3) Turbine pump4) Diaphragm pump5)Venturi pump

Types of Vacuum Pumps According to Displacement:1) Positive displacement2) Non-positive displacement

1) Positive displacement vacuum pumps:

1) Oil-lubricated2) Oil-less

Oil-lubricated pumps have higher efficiency, able to run at high vacuum pressures and have longer life than oil-less pumps. Oil-less pumps are cleaner, require less monitoring and maintenance.Mainly two type pumps of Positive displacement vacuum pumps are used for VBS, the reciprocating piston type and the rotary vane type are most common. Piston pumps are able to generate higher vacuums than rotary vane pumps, accompanied by higher noise levels and vibration. Rotary vane pumps may generate lower vacuums than piston

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pumps. But they offer several advantages over piston pumps. While their vacuum ratings are higher, they are able to move more air for a given vacuum rating.

2)Non-Positive displacement vacuum pumps:Non-positive displacement vacuum pumps have high CFM ratings, but generally at vacuum pressure levels too low for most vacuum bagging. A vacuum cleaner is an example of a non-positive displacement or turbine type pump.

2.2.2 VACUUM BAGGING MATERIALS AND PLUMBING SYSTEM:

Fig 2.2 Schematic Showing Materials in Vacuum bagging System

1)PEELPLY(RELEASEFABRIC):When the FRP Composite is laid down in the mould, we start applying. Peel ply is the first fabric to be placed inside the Vacuum bag. Peel ply is a woven fabric mainly of nylon. It sticks with the composite laminate but it can be pulled without discomfort. It’s often impregnated with the releasing agent

2)PERFORATEDFILM:These are used in combination release fabric, while perforated film is holding the resin

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in the laminate when vacuum pressure is used. Perforated films have holes in it which are dependent upon the resins characteristic of viscosity.

3)BREATHER MATERIAL:Breathers are non-woven materials that are placed on top of the perforated film to disperse vacuum over the entire part surface. Polyester breathers are used for low temperature/low pressure cures, and nylon breathers are for high temperature/high pressure cures.A breather (or bleeder) cloth allows air from all parts of the envelope to be drawn to a port or manifold by providing a slight air space between the bag and the

4)VACUUM BAG: The vacuum bag, in most cases, forms half of the airtight envelope around the laminate. If you plan to use vacuum pressure of less than 5 psi (10 hg) at room temperatures, 6-mil polyethylene plastic can be used for the bag. Clear plastic is preferable to an opaque material to allow easy inspection of the laminate as it cures. The vacuum bag should always be larger than the mold and allow for the depth of the mold.

5)MASTIC-SEALANT:Mastic Sealant is used to seal the vacuum bag in order to avoid any air leakage from the VBS is used to provide a continuous airtight seal between the bag and the mold around the perimeter of the mold.

2.2.3THE PLUMBING SYSTEM:The plumbing system provides an airtight passage from the vacuum envelope to the vacuum pump, allowing the pump to remove air from and reduce air pressure in the envelope. A basic system consists of :a) Flexible hoseb) Trapc) A portd)Control valve(Ball valve)e)Vacuum Throttle valve for controlling the VBS vacuum pressure.a)TRAP:A trap should be placed in the vacuum lines with the distance as close as possible to the VBS.The purpose of trap us to collect any resin so that it can’t get stuck into the vacuum lines, before it reaches the valves /pump.

b)VACUUM GAUGE:

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For measuring the vacuum level during the curing time of composite a vacuum gauge is a necessity. Mostly vacuum gauges indicate vacuum level in mercury inches form0 (one atmosphere to 30 inches below the one atmosphere).The negative pressure inside the VBS is equal to the pressure of atmosphere which is pressing it from outside of the bag.C)PORT:It is basically a suction cup used to connect vacuum bag with the exhaust tubing. It will be placed inside the vacuum bagging system (VBS) by cutting a slot in the vacuum bag to help drawing air from the composite laminate.D)VACUUMCONTROL VALVE:Control valve allows us to control the airflow in the envelope when placed into the vacuum lines. Air removal rate is affected by the vacuum control valve. The biggest demerit of this valve is that it can’t affect vacuum pressureE) VACUUM THROTTLE VALVE:Is used to control the vacuum pressure between vacuum control valve and VBS. This valve is used as an adjustable leak in the system to control the VBS pressure.

2.2.4VACUUMBAGGINGMOLDS:The mold surface must be airtight and smooth enough to prevent bonding to the laminate. Porous surfaces such as wood should be coated with epoxy or covered with a material such as plastic laminate to provide the necessary airtight surface. Each part produced in the mold will have a rough (bag) side and a smooth (mold) side. A colored gel coat can be applied before the laminate is laid in, leaving the outer surface of the laminate completely finished when it comes off the mold. The mold structure must be rigid enough to support the mold surface in its proper shape during the laminating process

TYPES OF MOLDS:

1)FLAT MOLDS:Flats molds are used to produce flat composites in form in order to produce different products including structural composites. Flats molds in form of tables can be used to produce multiple lay-ups of any sizes by vacuum bagging. Flat molds are simple 2)CURVED PARTS: Curved parts are used for the lamination over male/female molds. A female mold’s surface is generally concave, producing a laminated part with the smooth finish on the convex or outside—a boat hull for example. A male mold generally has a convex mold surface, producing a part with a smooth surface on the concave side.

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CHAPTER 3: CONCEPT EVALUATION

3.1 BASIC THEME FOR DESIGN SELECTION:As illustrated above that the vacuum pumping system is the main heart of vacuum bagging system. As the removal of air bags inside the laminate depends upon the pumping power of vacuum pump use in vacuum bagging system. If the shape of the mold is complex more power is required to required to remove the air bubbles while in simple molds mostly used for flat shape panels less power is required. So the design evaluation will be done on the basis of vacuum pumps used in the system.In vacuum bagging system the positive displacement pumps are mostly used for the generation of vacuum. So that’s why we will evaluate our design on the basis of types of positive displacement pumps.3.1.1 DESIGN CONCEPT 1- USE OF ROTARY VANE PUMP:

INTRODUCTION: There are three major components of rotary vane pump 1) the rotor2) the liner3)multiple vanes. Rotor and vanes are encased by the liner which slides into the designated slots of rotor. Vanes are pushed towards the outside, when the rotor is in spinning motion, thus a seal is created between rotor and surrounding liner. Thus in turn also creating a vacuum which helps in our motive of drawing gases through intake valve of the rotary vane pump and forces them out through the out take valve which is in the opposite direction of rotor.ADVANTAGES: There are many advantages of using rotary vane pump:

Cost is low Contamination resistance is high Reliability is quite high Maintenance is negligible Applicable for most vacuum bagging systems in world wide practrices Useful vacuum level is maintained while tolerating high amount of leaks Air removal rate is fast Smooth running

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DISADVANTAGES:

Higher level of vacuum can’t be generated Complex moulds can’t be used while operating with rotary vane pump.

3.1.2 DESIGN CONCEPT 2- USE OF PISTON PUMP:

INTRODUCTION:

Reciprocating-piston pumps are used to generate vacuum levels higher in different working conditions. All Reciprocating-piston pumps have one or more pistons linked to a rotating crankshaft. The alternating piston action moves air past check valves in the cylinder head which creates high level of vacuum at the inlet.

Lubricated piston pumps are quieter ,capable of producing less vibration, with higher capacity rating and have more life then the piston pumps higher capacity, and feature a much longer life than oil less piston pumps, but they have the disadvantage of being more heavier and expensive then the oil-less system.

ADVANTAGES OF PISTON PUMPS:

Can generate higher level of vacuum Mostly used in vacuum bagging system with complex moulds.

DISADVANTAGES OF PISTON PUMPS:

High initial cost comparatively to rotary vane pumps High maintenance is required Require more power to operate Produce higher vibration and high noise level Removal rate of air from the system is comparatively less than rotary vane

pump

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3.2 WEIGHTING AND RATING MATRIX FOR SELECTING VACUUM PUMP

SELECTION PROCEDURE 1. Two matrix structures have been utilized to choose Vacuum Pumps

2. The weighting matrix assesses the relative importance of selected technical criteria.

Table 3.1Design factors Legends

Cost ASafety BPower C

Maintainability DPerformance E

Reliability F

3.The individual demands were compared with each other and the matrix was constructed. Each row was compared with each column and if a row objective was considered more important than a column objective a ‘1’ was entered in a relative position in the matrix. If considered less important, then ‘0’ was entered.

4.The next step is to compare and score each of the available vacuum pumps in the weighting matrix. Each vacuum pump is rated on how well it fulfills the required criteria.

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3.2.1 WEIGHTING MATRIX FOR SELECTING VACUUM PUMP

Table 3.2A B C D E F TOTAL WEIGHTING

A 1 1 1 0 1 4 0.266B 0 1 1 0 1 3 0.2C 0 0 0 0 1 1 0.066D 0 0 1 0 1 2 0.133E 1 1 1 1 0 4 0.266F 0 0 0 0 1 1 0.066

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WEIGHTING MATRIX FACTORS:A CostB SafetyC PowerD MaintainabilityE PerformanceF Reliability

CONCEPT NUMBER LEGEND:0 Less Important1 More Important

RESULTHence the desirable characteristics are cost, safety and performance.

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3.2.2 RATING MATRIX FOR SELECTING VACUUM PUMP

Table 3.3Design

FEATURESweighting Design 1 Design 2 Design 1 Design 2

A 0.266 3 1 0.798 0.266B 0.2 3 2 0.6 0.4C 0.066 2 1 0.132 0.066D 0.133 3 2 0.399 0.266E 0.266 2 1 0.532 0.266F 0.066 2 3 0.132 0.198

2.593 1.462

RATING MATRIX FACTORS:A CostB SafetyC PowerD MaintainabilityE PerformanceF Reliability

CONCEPT NUMBER LEGEND:1 Less Important2 More Important3 BEST

RESULT As shown by the rating matrix, Design 1 i.e. Rotary Vane pump is more preferred over the other design.

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CHAPTER 4: FIBERS REINFORCEMENT

4.1 DIFFERENCE BETWEEN POLYESTER AND EPOXY RESINS:

4.1.1 POLYESTER RESINS:

Polyester resin is only compatible with fiberglass fibers and is best suited to building things that are not weight sensitive. It is also not tough and fractures easily. Polyesters tend to end up with micro-cracks and are tough to re-bond and suffer from osmotic blistering when untreated by an epoxy resin barrier to water.

Polyester resins such as these are of the ‘unsaturated’ type. Unsaturated polyester resin is a thermo set, capable of being cured from a liquid or solid state when subject to the right conditions.

4.1.2 TYPES OF POLYESTER RESINS:

There are two principle types of polyester resin used as standard laminating systemsin the composites industry.

1)Orthophthalic polyester resin 2)Isophthalic polyester resin

Fig 4.1 Idealized Chemical Structure of Typical Isophthalic Polyester

Most polyester resins are viscous, pale colored liquids consisting of a solution of polyester in a monomer which is usually styrene. Polyester resins have a limited storage life as they will set or ‘gel’ on their own over a long period of time. Often small quantities of inhibitor are added during the resin manufacture to slow this gelling action.

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Catalysts are added to the resin system shortly before use to initiate the polymerization reaction. The catalyst does not take part in the chemical reaction but simply activates the process. An accelerator is added to the catalyzed resin to enable the reaction to proceed at room temperature and/or at a greater rate.The molecular chains of the polyester can be represented as follows, where ‘B’ indicates the reactive sites in the molecule.

Fig 4.2 Schematic Representation Polyester Resin (Uncured)[From Sp guide to composites]

With the addition of styrene ‘S ‘, and in the presence of a catalyst, the styrene crosslink the polymer chains at each of the reactive sites to form a highly complex three-dimensional network as follows:

Fig 4.3 Schematic Representation Of Polyester Resin (Cured)[From Sp Guide to composites]

The polyester resin is then said to be ‘cured’. It is now a chemically resistant (and usually) hard solid. The cross-linking or curing process is called ‘polymerization’.

Great care is needed in the preparation of the resin mix prior to molding. The resin and any additives must be carefully stirred to disperse all the components evenly before the catalyst is added. This is especially so when laminating with layers of reinforcing materials as air bubbles can be formed within the resultant laminate which can weaken the structure.

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4.1.3 EPOXY RESINS:

Epoxies differ from polyester resins in that they are cured by a ‘hardener’ rather than a catalyst. The hardener, often an amine, is used to cure the epoxy by an ‘addition reaction’ where both materials take place in the chemical reaction.

4.1.1 RESIN COMPARISON SUMMARY:

Table 4.1 Advantages and Disadvantages of Polyester and EpoxyAdvantages Disadvantages

Polyester Easy to use Lowest cost of resins available

Moderate mechanical properties

High cure shrinkage Limited range of working

times

Epoxy High mechanical and thermal properties

High water resistance Critical mixing

More costly Difficult to handle

Table 4.2 Comparison between Polyester and Epoxy

Curing time Adhesion Easy to handle

Toughness Health Hazards

Cost

Polyesters ** ** **** *** ** *Epoxy **** *** ** **** **** ***

Where the number of“*” represent the weight age of the represented quality.

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4.2 WEIGHTING AND RATING MATRIX FOR POLYESTER AND EPOXY RESIN

4.2.1 WEIGHTING MATRIX FOR POLYESTER AND EPOXY RESIN

Table 4.3WEIGHTING MATRIX FOR POLYESTER AND EPOXY RESIN

Criteria A B C D E F Total WeightingA 1 1 1 1 0 4 0.2666B 0 0 0 1 0 1 0.0666C 0 1 1 0 0 2 0.1333D 0 1 1 0 0 2 0.1333E 0 0 1 0 0 1 0.0666F 1 1 1 1 1 5 0.3333

15

WEIGHTING MATRIX FACTORS:A CostB AdhesionC Easy to handleD ToughnessE Curing timeF Safety from Health Hazards

CONCEPT NUMBER LEGEND:0 Less Important1 More Important

RESULT:Hence the dominating characteristics are costand safety from health hazards.

And as we are fabricating the project for the composite material laboratory in future the student will perform the practical so we have made the safety our first preference and due to low budget the cost of the system is the second preference.

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4.2.2 RATING MATRIX FOR SELECTING RESIN SYSTEM

Table 4.4RATING MATRIX FOR SELECTING RESIN SYSTEMCriteria Weighting Resin 1 Resin 2 Resin 1 Resin 2

A 0.2666 3 1 0.7998 0.2666B 0.0666 1 2 0.0666 0.1332C 0.1333 3 1 0.3999 0.1333D 0.1333 1 3 0.1333 0.3999E 0.0666 2 1 0.1332 0.0666F 0.3333 3 1 0.9999 0.3333

2.5327 1.3329

RATING MATRIX FACTORS:A CostB AdhesionC Easy to handleD ToughnessE Curing timeF Safety from Health Hazards

CRITERION NUMBER LEGEND:1 Less Important2 More Important3 Most Important

RESULT:As shown by the rating matrix, Resin 1(Polyester) is more preferred over the

other resin (Epoxy).

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4.3 REINFORCEMENT:4.3.1 REINFORCEMENT TYPES:There are three main categories of fibers1) GLASS REINFORCEMENT2) CARBON REINFORCEMENT3) ARAMIDREINFORCEMENT

1) GLASS REINFORCEMENT:

Glass fibers manufactured from E glass are the most common reinforcing material. The physical properties correspond to those of metals (e.g. aluminum alloys), but the specific gravity of the laminates is lower than that of metals.

2) CARBON REINFORCEMENT:

Carbon fiber has the highest specific stiffness of any commercially available fiber, very high strength in both tension and compression and a high resistance to corrosion, creep and fatigue. Their impact strength, however, is lower than either glass or aramid.

3) ARAMID REINFORCEMENT:

Agamid fiber is a man-made organic polymer .They has high strength and low density giving very high specific strength. All grades have good resistance to impact. Compressive strength, however, is only similar to that of E glass.

4.3.2 FABRIC TYPES CATEGORIZED BY ORIENTATIONS:

There are three main categories of fibers according to orientation are1) UNIDIRECTIONAL2) BIAXIAL3) CHOPPED STRAND MAT

1) UNIDIRECTIONAL REINFORCEMENT (NON-WOVEN):

A unidirectional (UD) fabric is one in which the majority of fibers run in one direction only. A small amount of fiber or other material may run in other directions with the main intention being to hold the primary fibers in position, although the other fibers

34

may also offer some structural properties.

2) BIAXIAL REINFORCEMENT (WOVEN):

For applications where more than one fiber orientation is required, a fabric combining and fiber orientations is used. There are few kinds of fibers, each of them varies

there style according to the engineering applications.

3) CHOPPED STRAND MAT:

Chopped Strand Mat (CSM) is a non-woven material which, as its name implies, consists of randomly orientated chopped strands of glass which are held together by a PVA emulsion or a powder binder.

4.4 WEIGHTING AND RATING MATRIX FOR CARBON FIBER AND GLASS FIBER4.4.1 WEIGHTING MATRIX FOR CARBON FIBER AND GLASS FIBER

Table 4.5WEIGHTING MATRIXES FOR CARBON FIBER AND GLASS FIBERCriteria A B C D E Total Weighting

A 0 0 1 0 1 0.1000B 1 1 1 1 4 0.4000C 1 0 1 1 3 0.3000D 0 0 0 1 1 0.1000E 1 0 0 0 1 0.1000

10

WEIGHTING MATRIX FACTORS:A Cost D Low DensityB Fire Resistance E Impact StrengthC Electric Insulation

CONCEPT NUMBER LEGEND:0 Less Important1 More Important

RESULT:Hence the dominant characteristics are fire resistance and electric insulation.

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4.4.2 RATING MATRIX FOR CARBON FIBER AND GLASS FIBER

Table 4.6RATING MATRIX FOR CARBON FIBER AND GLASS FIBERCriteria Weighting Glass fiber Carbon

fiberGlass fiber Carbon fiber

A 0.1000 3 1 0.3000 0.1000B 0.4000 3 2 1.200 0.8000C 0.3000 3 1 0.9000 0.3000D 0.1000 2 3 0.2000 0.3000E 0.1000 2 1 0.2000 0.100

2.8000 1.600

RATING MATRIX FACTORS:A Cost D Low DensityB Fire Resistance E Impact StrengthC Electric Insulation

CRITERION NUMBER LEGEND:0 Less Important1 More Important2 BEST

RESULT:Hence the desirable characteristics are fire resistance and electric insulation.

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CHAPTER 5: COMPONENTS USED IN THE PROJECT

The components that are being used in our projects are divided in three categorizes Fabrics and Films Reinforcement and Chemicals Mechanical Components

5.1 FABRICS AND FILMSThe following table shows the material of the fabrics and films that is available in

local market. These materials that we are using have the same function as described in previous chapter. Table 5.1 FIBRES THAT ARE AVAILABLE IN LOCAL MARKET

FABRICS AND FILMS MATERIAL OF THE FABRICS AVAILIBILTY IN LOCAL MARKET

Breather/bleeder Polyester yarn YesPerforated film Polyethylene Yes

Vacuum bag Polyethylene bag YesRelease fabric Nylon YesMastic sealant --------- Yes

5.2 REINFORCEMENTS AND CHEMICALS

The following table shows the material of the fabrics and films that is available in local market. These materials that we are using have the same function as described in previous chapter.

Table 5.2REINFORCEMENTS AND CHEMICALS AVAILABLE IN LOCAL MARKETREINFORCEMENT AND

CHEMICALSTYPE AVAILIBILITY IN LOCAL

MARKETGlass fiber E glass Yes

Gel coat Polyester YesResin Polyester Yes

Catalyst MEKP YesReleasing agent Silicon resin Yes

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5.3 MECHANICAL COMPONENTSWe have made our plumbing system according to the material that is available in

the local market.Table 5.3MECHANICAL COMPONENTS, THEIR MATERIAL AND THEIR AVAILIBILITY

MECHANICAL COMPONENTS MATERIAL AVAILIBILITY IN LOCAL MARKET

Vacuum Hose Rubber YesVacuum Port Brass Yes

Vacuum Throttle Valve Brass YesControl Valve Brass YesVacuum Pump ------ YesVacuum Gauge ------- Yes

5.4. COST ANALYSISAs we have purchased our all the mechanical components and the films from the

local market and didn’t import any of the product, so that’s why we have made considerable amount difference.

Table 5.4 MECHANICAL COMPONENTS

ITEMS Prices (Local) PKR

Prices (International) US$

Prices (International) PKR

Vacuum Pump 3500 317.87 27200Vacuum hose 400 64.50 5500

Vacuum gauge 500 23.60 2000Throttle Valve 1000 29.15 2500Control valve 500 29.15 2500Vacuum port 50 46.5 4000

Mold 1000 ----- -----Resin Trap 300 89.00 7650

Sub Total (a) PKR 7120.00 US$ 599.77 PKR 51350.00

FABRICS AND RESINSITEMS Prices (Local)

PKRPrices (International)

US$Prices (International)

PKRReleasing agent 300 16.84 1450

Vacuum bag 100 20.35 1750Perforated film 150 7.25 625Release fabric 150 9.3 800

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Mastic sealant 50 7.09 600Fiber glass reinforcement 400 10.54 900

Gel coat 350 26.67 2300Polyester 200 12.47 1000

CATALYST(MEKP) 50 9.47 800Breather 150 5.85 500

Sub Total (b) PKR 1800.00 US$ 125.83 PKR 11325.00

TOTAL COSTITEMS Prices (Local)

PKRPrices (International)

US$Prices (International)

PKRSub Total (a) PKR 7120.00 US$ 599.77 PKR 51350.00Sub Total (b) PKR 1800.00 US$ 125.83 PKR 11325.00

Total PKR 8920.00 US$ 725.60 PKR 62675.00

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CHAPTER 6: FABRICATION DETAIL

Fabrication of a vacuum bagging system is divided into three major portions:1)Plumbing System2)Fabrics3)Chemicals and Reinforcements

6.1 PLUMBING SYSTEM:

Plumbing system consists of: A) Vacuum PumpB) Vacuum GaugeC) Vacuum HoseD) Vacuum Control ValveE) Vacuum PortF) Vacuum Throttle ValveG) Metallic PipingH)Vacuum FittingsI)Resin Trap

A) VACUUM PUMP:

The first step in producing a vacuum bagging system is to choose a pump that can fulfill can our need of producing enough vacuum pressure to help remove air bags from the vacuum bagging system. As we had earlier mentioned in the design phase that for removing the air bags from the laminate we would prefer using Positive displacement Rotary vane vacuum pump.

PUMP RATINGS:

Motor Power .3620 HpAir capacity(CFM) 3.037CfmUltimate pressure 8 KpaType of Pump Oil Less Vacuum PumpFrequency 50-60 Hz

BAG size, ultimate pressure and desired vacuum rate must be matched with the vacuum

40

pump in order to get the best results. Also, if a leak is present in a system which exceeds the CFM rating of the pump, even a partial vacuum will be difficult to achieve. By trying to reduce as much as air in the vacuum bag before sealing it and applying vacuum, vacuum pump will have to work less in order to remove the air from the bags.

Fig 6.1Vacuum Pump

B)VACUUM GAUGE:We will be using a bourdon type-vacuum gauge for monitoring vacuum system operation and its performance. The deformation of curved elastic bourdon is the basis of the measurement of vacuum pressure when vacuum is applied to the gage's port. The dial faced vacuum gauge is capable of displaying vacuum from 0 to 30 hg. It’s in diameter and can be placed in specific areas to measure vacuum pressures in the vacuum bagged assembly.

Fig 6.2Vacuum Gauge

C) VACUUM HOSE:

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Vacuum hose which we are using is made up of rubber tubing and is used to connect Vacuum Pump with other components of Plumbing system. Vacuum hose which we are using is compatible with the resin system and doesn’t contain any pinholes to help avoiding air leakage. It should be stiff to resist vacuum pressure since it will also be evacuated.

fig6.3 Vacuum HoseD) VACUUM CONTROL VALVE:

A ball valve will be used as control valve. It is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked.

Fig 6.4 ball valve

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E) VACUUM PORT:It is basically a suction cup used to connect vacuum bag with the exhaust tubing. It will be placed inside the vacuum bagging system (VBS) by cutting a slot in the vacuum bag to help drawing air from the composite laminate.

F)VACUUM THROTTLE VALVE: We will be using Globe valve as a Vacuum Throttle valve for the purpose of controlling vacuum pressure in the vacuum bagging system. Globe valves control the vacuum pressure by reducing the air flow rate

FIG 6.5 VACUUM THROTTLE VALVE

G) METALLIC PIPING:Metallic piping of Galvanized Mild Steel is used to connect different parts in the assembling of plumbing system for the vacuum bagging system (VBS).Vacuum Control valve, Vacuum throttle valve, Vacuum gage and Vacuum Hose are interconnected by the piping while maintaining the adequate air flow.

H)VACUUM FITTINGS:Vacuum Fittings(Tees, Elbows and adapters ETC) are used to Connect metallic piping with PLUMBING SYSTEM in order to adapt to requirements of shape and sizes ,while making sure of regulating the flow of air in the vacuum bagging system.

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FIG 6.6 VACUUM FITTINGS

I)RESINTRAP: Locally manufactured Resin trap is used to collect excess resin flowing out form the composite laminate and stops it to reaching the vacuum lines in order to protect the vacuum PUMP, otherwise resin reaching Vacuum Lines would stop the Vacuum pump from drawing air from VBS

Fig 6.7RESIN TRAP

6.2 FABRICS, FILMS AND MOULD:

As the fabrics involved in vacuum bagging system are not available commercially in local market so we used alternate fabrics to perform the specific operations

A)VACUUM BAG FILM:

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We used polyester film as a vacuum bag film as it is easily available in the local market and can be easily used for the vacuum bagging of flat panels of fiber reinforced composites.

B)PERFORATED FILM:Polyester film was used as a Perforated film which is slightly porous to allow the passage of only air through it while preventing the further flow of matrix.

C)RELEASE FABRIC:Nylon fabric was used for as a release fabric for the purpose of separation between breather and laminate.

D)BREATHER FABRIC:Fabric of polyester was used as a breather fabric for our vacuum bagging system. These provide the mean of the vacuum and a path of gas glow over the laminate while assisting removal of air from the whole assembly and maintaining the uniform vacuum pressure.

E)MASTIC SEALANT:It is used to seal the bag to apply the removal of air from the vacuum bag. And to make system air tight so that outside air can’t penetrate the Bag thus weakening the strength of composite panels. Also mastic prevents the air leakage from the vacuum bagging systemF)MOULD:Mould is basically the same as the finished product we require in form of Flat panel. Mould of wood would be used for the purpose of preparing the fiber reinforced flat panels

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6.3ASSEMBLING OF VBS (VACUUM BAGGING SYSTEM):

The mechanical components and fabrics are placed according to their positions as shown in design drafts from Appendix. It is ensured that resin trap doesn’t allow any amount of resin passing from it; otherwise the buildup of resin/catalyst mixture in vacuum lines would prevent the System to perform the desired function that is to remove air bubbles. Also there is proper sealing between the components of plumbing systems to make sure that there is no leakage in the vacuum bagging system. Leakage prevention is especially important with vacuum systems because even very small leaks can greatly diminish performance and efficiency.

FIG 6.8 PLUMBING SYSTEM

6.4CHEMICALS AND RESINS:

A)RELEASING AGENT (MOLD RELEASE):For the protection of mold surface while we are removing the finished composite flat panel a releasing agent is used. It will also help in reducing imperfections in the molded surface.B)GELCOAT: For the high quality finish of fiber reinforced composite flat panels Gel coat will be used. Gel coat is applied to applied prior to the start of Vacuum bagging process

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C)CATALYST:For producing a fiber reinforced composite laminate resin must be cured with catalyst. Thus by adding catalyst to resin the curing reaction will start at room temperature. Basically catalyst is used to improve the curing rate for the composite laminate

D)ACCELERATOR:Polyester resin which we used was not pre-accelerated ,therefore accelerators were used to speed the curing reaction for catalysed polyester resin at room temperature

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CHAPTER 7: CALCULATIONS

7.1 CALCULATING LAMINATING RESINS:

Resin/Hardener required (g)

,7.2 CALCULATING GELCOAT AND COATINGS:Gelcoats required =Where A=Area to be coated t=total finished thickness required

=Density of Polyester/MEKP matrix A=0.1451

1.12 g/cm3

t=254µm=

*Assuming 50% wastage for resin residue left on tools

7.3 CALCULATING FIBRE VOLUME FRACTION FROM GIVEN FIBRE WEIGHT FRACTION:

2.6

=

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7.4 CALCULATING CURED PLY THICKNESS:

7.5 CALCULATING THE DENSITY OF FIBER-REINFORCED COMPOSITE:

By using above equation

7.6 RULES OF MIXTURES:Rules of mixtures mathematical expressions which give some property of composite in terms of properties, quantity and arrangement of its constituents.

7.6.1 MICROMECHANICAL MODELS OF STIFFNESS:

Unidirectional Fibers are the simplest arrangement of fibers to analyze.Unidirectional fibers provide maximum properties in fiber direction, butminimum properties in transverse direction

Fig 7.1Fiber (longitudinal) and transverse direction

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7.6.2 TENSILE MODULUS:The tensile modulus are different in diffenrent direction.In the model given below the tensile moduli are represented by and ,where and represents respectively the tensile modulus in longitudinal and transverse direction.

Fig 7.2 Tensile modulus in longitudinal and transverse direction

7.6.3 ASSUMPTIONS IN DEVELOPING RULE OF MIXTURES:We make following assumptions in developing rule of mixtures1. Fibers are uniform, parallel and continuous.2. Perfect bonding between fiber and matrix.3. Longitudinal load provides equal strain in fiber and matrix

7.7 CALCULATING (UD) PLY-LONGITUDINAL TENSILE MODULUS:

Tensile modulus For polyester resin =3.5-4.7 GPa=

Tensile modulus For E-glass =73 GPa=

7.8 CALCULATING (UD) PLY-TRANSVERSE TENSILE MODULUS:

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Fig 7.3 Graph between FVF and Tensile Modulus

BEHAVIOUR OF GRAPH BETWEEN FVF AND TENSILE MODULUSGraph between Fiber Volume Fraction and Tensile Modulus tells us about the behavior of three different type of glass fabrics designated by their orientations i.e1) UD or Unidirectional glass fabrics2) Biaxial or Woven Roving3) CSM or Chopped Strand MatBy studying the behavior of graph a conclusion can be drawn that by increasing the content of fiber volume the tensile modulus of polyester- resin matrix also increases

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thus the graph is varying linearly

7.9 CALCULATING COEFFICIENT OF LONGITUDINAL THERMAL EXPANSION:

=Coefficient of thermal expansion for E-glass=

=Coefficient of thermal expansion for Polyester=

7.10 CALCULATING COEFFICIANT OF TRANSVERSE THERMAL EXPANSION:

7.11 CALCULATING POISSON RATIO:

where

=Poisson ratio for glass-fiber=0.18=Poisson ratio for polyester matrix=0.33

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TABLE 7.1PARAMETERS IN TABULATED FORM:

S. No Parameters Symbol Calculated value Units

1 Amount of Laminating resin required

11.032236

2. Amount of gelcoat required 61.917

3 Fiber Volume fraction 0.3925

4. Cured ply thickness 18.6

5. Density of FRC 1.7009

6 Longitudinal tensile modulus 30.7785

7 Transverse tensile modulus 5.588211

8 Coefficient of longitudinal thermal expansion

9 Coefficient of transverse thermal expansion

10 Poisson ratio 0.271

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CHAPTER 8: STANDARD OPERATING PROCEDURES

Preparation of the materials to be laminated

We cut the fiberglass, breather, release fabric, perforated film, breather material and vacuum bag according to the sizes. In our experiment of our mold which was of 1x1 ft2.

Surface preparation

The surface of mold was thoroughly cleaned with emery paper to assure that the laminate will lie flat in the mold.

Application of gel coat and releasing agent

We first applied gel coat to the mold. The curing time of gel coat was 24 hours but we had to apply releasing agent when it was sticky for better experimental results. That’s why we waited only two hours and then applied releasing agent when it was not completely cured. The main purpose of gel coat was to give wooden mold a good surface finish as wood has lot of pores containing air bubbles which can create problems while doing vacuum.

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Fig 8.1Application Of Gel Coat On Mold

Fig 8.2 Application Of Releasing Agent On Mold

56

Mixing of resin with accelerator and catalyst

On the other hand in a bowl we added 5ml of accelerator in 1kg of resin and stirred thoroughly. After its mixing we added small amount of catalyst into resin and accelerator mixture. Care should be taken while adding catalyst as it needs to be stirred continuously otherwise it will get hard even in the bowl.

Placing of fiberglass The first layer of CSM (Chopped Strand Mat) fiberglass fabric was placed in position in the mold according to the mold size which was 1x1ft.Then a mixture of resin with catalyst and accelerator was applied to quicken our experiment. After that we put another layer of fiberglass and resin mixture one by one. We finally placed five layers of fiberglass and five times resin into the mold.

Fig 8.3 Placement Of Fiberglass reinforcement In Mold

Placing of release fabric

The release fabric layer was placed over the laminate. The release fabric was peeled off the cured laminate leaving a fine-textured surface & excess polyester resin which had bled through was removed along with.

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Fig 8.4 Placing release fabricPlacing of breather material

After placing release fabric we placed a layer of breather over release fabric and laminate.Breather Fabric is a polyester blanket that absorbs excess polyester resin, which pass through the release fabric and allows air to pass through its fibers to the port. When vacuum pressure is applied, it is necessary to press all of the layers of material into contact with the mold to avoid “bridging”

Fig 8.5 Placing breather material over Release fabric

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Placing of perforated film

Over breather we placed a perforated film that was helpful to support the laminate.

Fig 8.6 Placing Perforated filmPlacing of mold with laminate into vacuum bag

By placing release fabric, breather and perforated film over the laminate, we placed the whole mold into the vacuum bag and overlapped the ends to ensure that there are no gaps sealed it with mastic sealant forming a continuous airtight seal in order to get a good vacuum pressure. While cutting the bag, we allowed excess (at least 20% larger) bag material within the sealant perimeter to avoid stretching the bag or bridging areas when the vacuum is applied.

Connecting the vacuum line to the bagWe punctured a small hole in the bag and attached the port to the bag over the hole. Port is a suction pipe fitting with a hole through it. We connected the vacuum line to the bag through this port. Breather fabric provides a path inside the bag through the port to the vacuum. One or two extra layer of breather can be place under the port but in our experiment we have used one layer of breather film under the port. For larger parts multiple ports are prefer to be fixed.

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Fig 8.7 Connecting vacuum line with Vacuum Bag,Evacuation of air from the bag

The evacuation of air from the bag was started by turning the vacuum pump on. The vacuum was temporarily shut off to reposition laminate or adjust the bag & checked any leakage around the bag perimeter, at folds (pleat) in the bag, laps in the mastic, port connection or in the vacuum line. We rectified the leakage by plugging with pieces of mastic.

Observation of Vacuum gauge

The vacuum pump was started that read the vacuum gauge in psi unit (or mbar). We observed that our gauge was showing 6psi vacuum pressure.

Curing of laminate and separation from the vacuum bag

Allowed the laminate to cure about 45 minutes, and then turn off the vacuum pump.

After curing, the vacuum bag breather and release fabric were removed. The laminate was separated from the mold carefully using small wedges between edge of the laminate and the wooden mold.

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Fig 8.8 Removing Fabrics and Vacuum Bag from laminate

Fig 8.9 Cured laminate Of Chopped Strand Mat

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CHAPTER 9: SAFETY MEASURES, RISK ASSESSMENT AND RECOMMENDATIONS

9.1 SAFETY MEASURES:

1) VENTILATION:

There must be adequate ventilation in the area of working. Prolonged and repeated exposures to high concentrations of fumes from resins and other chemicals can result in health problems. There can also be immediate problems, such as skin and eye irritations

2) PROTECTIVE CLOTHING AND EQUIPMENT:

Wear protective clothing and equipment while handling and using fiberglass reinforcing materials. Fine glass threads and particles from glass fiber reinforcing materials can be irritating to the skin, respiratory system and eyes. Exposure can result in allergic reactions, and other problems. Prevention should be adopted to minimize or eliminate contact between glass fiber material and body. Do not handle fiberglass reinforcing materials with bare hands.

3) AVOID OPEN FLAME HEATERS:

Don’t use open flame heaters while working fiber glassing working areas. If heating is necessary make certain that the heater used for the purpose of heating doesn’t start a fire and explosion hazard with chemicals and materials being used. Same principle is maintained for the heating devices which will be used for increasing the curing rate

4) KEEP CHEMICALS AWAY FROM FLAME:

Keep resins, catalysts and other fiber glassing chemicals away from fire and flame. Polyester resins are flammable in both liquid and cured states. Due to danger of spontaneous combustion, proper storage of chemicals should be done. Heat from fire or flame can cause catalysts for polyester resins to explodeNever smoke while using the chemicals and resins for producing the fiber reinforced composite panels

5) HAND CONTACT EXPOSURE:

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It is most common when using composites. The use of proper protective gloves is important to control exposure. A selection of gloves used for protection against exposure to chemicals. Depending on the permeability of the glove material to the chemical used, the glove chosen will protect the wearer for only a limited time.

6) EYE PROTECTION:Eye protection should be selected based on impact (flying particles) and/or chemical splash possibilities. Selections should include appropriate safety glasses, goggles, face shields or a combination of these. If organic peroxides do come into contact with the eyes, they can cause serious injury if not treated immediately.

7) STORAGE:

Resin should be stored in the dark in suitable closed containers. Ideally, containers should be opened only immediately prior to use, and should never be left open. Where containers have to be stored outside, they should be protected from possible early polymerization from the effects of direct sunlight.

The storage (or shelf) life of polyester resins is three months for pre-accelerated systems, and 6 months for non-accelerated systems, provided that the resin is stored below 20ºC in unopened containers. Storage at higher temperatures will considerably reduce the shelf life. Most catalysts are organic peroxides and present a possible fire hazard. They should be stored in a separate area in a cool, well ventilated, fire resistant compartment.

All reinforcements should be stored in their original packaging in a warm, dry and dust free environment.

8) OTHER CONSIDERATIONS:

1)Never mix an accelerator with a Catalyst for e.g. MEKP to avoid any explosion2)Never use metal containers for storing Methyl Ethyl Ketene Peroxide(MEKP) as danger of spontaneous explosions occur due to contact of catalyst with metal container3) Always have one or more fire extuingshers handy in the lab in case of fire emergency.4)Empty containers retain vapors and product residue and therefore are potentially explosive and/or may contain toxic vapor hazards.

9) SAFETY CONSIDERATIONS FOR VACUUM PUMPS:

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1) Make sure that switches and electric cords are defect free.2) Never use pumps near flammable chemicals or combustible materials.3) Avoid placing of pumps in unventilated cabinet which in turn allows heat and exhaust to build.4) Use shortest length of tubing that reaches where needed.5) Never use solvents which can damage the pump.

9.2 PROJECT RISK ASSESSMENT:

Risks are basically defined as the event or the circumstances that occurs without the willing and cause the delay and the termination in the project. The risk assessment has a really importance in the project. In other words the risks are combination or constraints and the uncertainty. The constraints are difficult to remove but they have to be understood.

The risks analysis is carried out to find out the different risks assessment and finding out the way to solve them completely of finding out the other way out. This analysis is carried out using three point process that are illustrated below

Risk assessment Risk analysis Risks avoidances

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Our groups listed the number of risks and discussed the resulting consequences. The likelihood and impact of the risks are rated on low, medium and high basis.The risk rating is subsequently calculated by multiplying the impact and likelihood values.

RISK CONSEQUENCES

RISK

LIKE

LIN

ESS

RISK

IMPA

CT

RISK

RAT

ING RISK

MANAGEMENT

Cost Project may be exceed from the

budget

1 2 2 Avoid over expenses and products from local

marketSafety Measures Chemicals used in

the projects are toxic

1 3 3 Special safety equipment should be

used like gloves, goggles, face masks

Health Measures The fumes of the chemical are toxic

for health.

1 2 2 Ventilation system should be installed.

Manufacturability

All the projects are not manufactured in

local market

1 3 3 Already manufactured products should be

usedTime Factor Project may not be

completed in desired time period

1 2 2 Try to complete every task before the

assigned period in the Gantt chart.

Personal risk Project members are not available due to personal

matters like sickness etc

2 3 6 Care of the health should be taken.

Lack Of Publicity People may not be aware of project

1 1 1 Marketing should be attractive and informational.

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9.3 FUTURE RECOMMENDATIONS:

We have successfully completed our project according to our project requirement (the preparation of flat panels) but still the improvements can be made in our projects and we have a lot of future recommendations.

The chemical that are being used like polyester, catalysts, glass fibers, fibers etc are consumable and should be bought from time to time. The chemicals are easily available from PRIME CHEMICAL, JORIA BAZAR KARACHI PAKISTAN. And the fabrics are easily available from the BOLTAN MAKET KARACHI.

We worked on the glass fibers, and it is also possible work on the carbon fiber. Right now the vacuum bagging system which we used is just for the making of

simple flat panel of fiberglass reinforced composite laminate It can be used for the manufacturing of complex glass fibers panels by changing

the mould The desired complexity of the panel can be achieved if the pump of the higher

horse power rating is used As the pump we have used is the oil less pump, so the pump does not require the

maintenance We have used polyester as resin matrix but epoxy can also be used in it. The resin, we are using isn’t pre accelerated. So the catalyst can be used with the

pre accelerator. The mould we are using is made up of wood so that’s why we have to use the gel

coat also to make it air tight but if we will use the mould made up of metal then gel coat will be no more required.

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APPENDIX A

STATEMENT OF REQUIREMENT(SOR)

Title1. Design and make a Vacuum

Bagging System for the composite Laboratory for preparing multiply fabric reinforced composite material flat panels.

Issue: 01 Date: 27-03-2010

CHANGES D/W REF REQUIREMENTS

1 Introduction 1.1 Preamble Composite materials are the ultimate solution

to fulfill the material requirements in the future. It is not only needed for an alternative to the materials being used but also fulfills the special technical requirements which are not exhibited by the materials already being used. Composites have very wide scope in aerodynamic technology specially, in space technology.

The objective of the project is to design and fabricate a vacuum begging system for the composite laboratory for preparing composite materials. This will provide a base for development of different composite materials in the lab for specific requirements. Composite materials have gained popularity in high-performance products that need to be

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lightweight, yet strong enough to take harsh loading conditions. Such as Composite materials have gained popularity in high-performance products that need to be lightweight, yet strong enough to take harsh loading conditions. such as

1.2 Scope

1.2.1 Wide Applications are aerospace components (tails, wings, fuselages, and propellers), boat and scull hulls, bicycle frames and racing car bodies. Instead of above, composite shave applications in other products also.

1.3 Related Documents

1.3.1 Books

Hand book of composite by GEORGE LUBIN

Composite Manufacturing by SANJAY KMAZUMDAR

1.4 SymbolsFrom the D/W column of this table

D Demand A mandatory requirement

W(H) Wish high A highly desirable attribute

W(L) Wish low A low desirable attribute

1.5 Deliverables

W(H) Easily usable System.

W(H) Preparation of some composites using the system.

W(L) Study properties of developed composites

D Final project report

2 Technical Requirements

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2.1 Knowledge of composites, Basic materials for composites preparation, Vacuum & pressure line components and their installation, properties of composites.

2.2 Design ConsiderationsDesign should be such that, it can be used for several preparations.Its vacuum & pressure can be controlled easily.

It should not be very expensive.

3 Miscellaneous 3.1 The Project Contents would be monitored by

the designated Project Advisor Dr.JoharKhurshidFarooqi

3.2 The group members are Mr.AsimIftikhar, Mr.NomanAbid, Ms. Urfa Rasool.

4 Hazards/SafetyGloves, goggles, are required while preparing composites,Proper ventilation is needed while chemical handling.

5 Costs

5.1 The estimated cost of the Project is Rs. 75,000.

5.2 The above mentioned cost is subjected to material cost, assembly requirements, and testing.

Project Advisor'sSignature

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APPENDIX B:

GANTT CHART

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APPENDIX CSPECIFICATIONS OF FIBER GLASS FABRICS

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Source: TECHNICAL FABRICS HANDBOOK BY HEXCEL

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APPENDIX C2MECHANICAL PROPERTIES OF E-GLASS FIBERS

Properties Symbol Unit E-glassDensity

Modulus of elasticity

tensile strengthPoisson ratio

Coefficient of thermal expansion

Source:R & G HANDBOOK

APPENDIX C3

MECHANICAL PROPERTIES OF POLYESTER RESIN

Properties Symbol Unit Resin/catalystDensity 1.12

Modulus of elasticity 3.5

tensile strengthPoisson ratio .33

Coefficient of thermal expansion

123.5

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APPENDIX DDESIGN DRAFT

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APPENDIX E

LAB MANUAL

AIM: To prepare fiber reinforced composites by using vacuum bagging system

EQUIPMENT:

Apparatus of Vacuum Bagging system consists of three major parts

1) FABRICS, MOLD AND REINFORCEMENTSA) Release fabricB) Perforated FilmC) Breather material D) Mastic SealantE) Vacuum Bagging filmF) Fiber Glass reinforcement

2) CHEMICALSA) Gel coatB) AcceleratorC) Resin MATRIXD) CatalystE) Releasing Agent

3) OTHER ACCESSORIESA) ScissorsB) BrushesC) Gloves

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SCHEMATIC DIAGRAM FOR VACUUM BAGGING SYSTEM:

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THEORY:

COMPOSITE:

Composite material consists of at least two materials which are combined to improve combined mechanical properties that would be different to properties if materials were used as the single entity. Mainly composite materials consist of Resin Matrix and a reinforcement .added to improve the strength and stiffness of matrix, While the reinforcement is usually in fiber forms

Composite are divided into three main types1) Polymers matrix composites also known as FRP or fiber reinforced composite panels2) Ceramic matrix composites3) Metal matrix composites

VACUUM BAGGING METHOD:

Vacuum Bagging System is a process which uses a two side mould to produce the Fiber reinforced composite panels. Lower side mold is rigid mainly made up of Wood while vacuum bag forms the upper to complete the mold. After completing the mold set vacuum pressure is applied on the system for improving consolidation of the composite and removing air bubbles of the Cured laminate of Fiberglass reinforced plastic. Process is mostly performed on ambient temperatures depending on the resin system used with the vacuum pressure acting on the system. Vacuum Pump or air compressor is used to extract air bubbles from the Vacuum bagging system.

PHASES DURING THE CURING OF POLYESTER RESIN:

Gel Time: Time required between the addition of curing agent and giving time for setting the resin to become a soft gel. On this stage liquid resin has lost its ability to flow viscousHardening Time: It’s the time when resin is hard enough and can be easily removed from the mouldMaturing Time: The time required for composite laminate to acquire its desired hardness and stability, This time can vary from few hours to weeks and it is solely dependent on Resin Matrix and the curing system used.

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PROCEDURE:

1) Cut the fabrics (Release, Breather) and films (Vacuum Bag and perforated film) according to requirement.2) Apply the gel coat to the mold 3) Apply the releasing agent to the mold before starting the vacuum bagging process4) Add accelerator with un-catalyzed-polyester resin and mix it. After mixing add the catalyst to accelerated polyester resin5) Place layers of CSM in the mold and apply Resin Matrix to it6) Place layers of release fabric, breather fabric and vacuum bag over the mold7) Connect Vacuum port with the vacuum bag by puncturing a small hole in it8) Turn the vacuum Pump on, to start the evacuation of air from the bag9) After curing, turn off the vacuum pump and remove the films and fabrics

PRECAUTIONS:

1) Adequate ventilation should be there in the lab2) Wear protective clothing3) Avoid bare hand contact with chemicals and fiber reinforcements 4) Keep chemicals away from flame in order to avoid fire explosion5) Avoid empty containers6) Never use solvents that can damage the Vacuum pump 7) Make sure that Switches and electric cords are defect free

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APPEDIX FPROCESS FLOW DIAGRAM

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REFERENCES AND RESOURCES

1. Small Boat Mechanics and Materials, Jerold Winger2. R&G Handbook Composite Materials3. Fabric Handbook March 20094. SP Systems Guide To Composites5. Construction Materials: Their Nature and Behavior, J. M. Illston, P. L. J. Domone6. Mechanics of Laminated Composite Plates and Shells, J N Reddy

ELECTRONIC REFRENCES7. http://www. tech . plym . ac . uk 8. http://www.aoc-resins.com 9. http://www.engineershandbook.com 10. http://fmgvacpump.com/rotary-vane-pump.asp 11. http://www.bertram31.com 12. http://www.fiberglast.com 13. http://www.fiberglasssupply.com 14. http://www.westsystems.com 15. http://www. wikipedia .org 16. http://machinedesign.com/article/vacuum-pumps 17. http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html 18. http://www.utexas.edu/safety/ehs/lab/vacuum_pump_safety.html 19. Crystic Handbook20. Vacuum Bagging Techniques by West systems21. Handbook Of Composites By George Lubin

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