final composites file9

DEPARTMENT OF MECHANICAL AND INDUSTRIAL ENGINEERING

Report for the course project, Dec 2011; MECH-6521

PRINCIPLES OF THE MANUFACTURING OF COMPOSITE MATERAILS

MECH 6521 FALL -2011

MANUFACTURINGOF

COMPOSITE CHAIR

SUBMITTED TO: DR. SUONG V. HOA

PROJECT COORDINATOR: DR.MING XIE

SUBMITTED BY: Asmita Dubey 9796924 Charanpreet Singh Heer 6420753 Israt Jahan Eshita 9806946 Rajan Gupta 5769035 Rohit Katarya 6306160 Vikas Pandit 6238394

Number of pages: 18

Number of words: 2325



ContentsObjective...........................................................................................................................................

1.Introduction.................................................................................................................................3

2.Experimental procedure in lying up and making the seat......................................................4

2.1.Selecting of material.............................................................................................................4

2.2.Cleaning the mould surface.................................................................................................4

2.3.Applying releasing agent......................................................................................................5

2.4.Placement of pre-pregs........................................................................................................6

2.5.Curing....................................................................................................................................7

3.Process Parameters, time, temperature, pressure...................................................................8

3.1.Quality of Part as measured by.............................................................................................

3.2.Optical microscope observation..........................................................................................8

3.3.Mechanical property from sitting test..................................................................................

4.Cost Estimation.........................................................................................................................15

5.Results............................................................................................................................................

6.Conclusions....................................................................................................................................

7.Appendix....................................................................................................................................17

References.....................................................................................................................................18



1. Introduction

Composite materials for construction, engineering, and other similar applications are formed by combining two or more materials in such a way that the constituents of the composite materials are still distinguishable and not fully blended. The two main constituents of composite materials include fiber and matrix. However, one can use fillers to add extra strength to the product. Each constituent of composite material has its own unique role to play.

A) Matrix in composite materials gives the shape to the composite part, protects the reinforcements to the environment, transfer loads to reinforcements.

B) The aim of reinforcements i.e. fibres, in composites are to get strength, stiffness and other mechanical properties, dominate other properties as coefficient of thermal extension, conductivity and thermal transport.

C) Fillers like glass wool and other Nano particles give such properties to the material that

makes it unique from the other metallic or non-metallic materials.

Therefore, Composite materials have excellent compressibility combined with good tensile strength [1]. Depending upon the type of geometry of product and type of resin used, there could be many different techniques of to manufacture the composite materials. Like hand layup, fiber or filament winding i.e. bradding, liquid composite molding (L.C.M), Pulltrusion, fiber placement etc. are some few techniques of manufacturing. The type of resin used tells us whether the process is going to be inside or out of autoclave. During the manufacturing, various defects like voids (porosity), Fibre wrinkling, Fibre misalignment, distortion, inadequate wetting out of fibres. [4] etc. could be faced. All of these defects reduce the performance and life of the product.

In the present project, as the geometry of product to be formed was not so complex. So, hand layup technique was employed. The resin used was polyester that makes the process out of auto clave. The glass fibers were used as a reinforcement material.



2. Experimental procedure in lying up and making the seat

2.1 Selection of material

Selection of materials and specimen is very important for the manufacturing of a good quality composite chair. In this project, glass fibre having plain weave fabrics and polyester along with Plastic mould of chair was used.“A plain weave fabric is made by interlacing yearns in an alternating over-and-under pattern. There is one warp fibre for one fill fibre without skipping. The pattern gives uniform strength in two directions.” The skins are made from glass fibres and polyester resins. Since the fabrics give uniform strength in two directions, we placed the layers over each other without changing the angle.

As per our requirement of making the chair that can bear the load of 80Kgs, we choose

A) Glass- fibres,for reinforcement as it is cheaper and strong enough to bear that much load.

Fig. 1 Glass fibre fabric

B) Polyester resin, provide better packing of the material and this in turn gives higher density, better strength, stiffness and environmental resistance and overall it does not need autoclave for its curing.

Fig. 2 polyester as a resin



C) Cobalt, accelerates the curing process, but it also reduces the pot life of the resin so we used it in a very small amount,

Fig. 3 cobalt

2.2 Cleaning the mould surface

The mould surface should be cleaned properly as the final surface finish depends on it. Otherwise, the surface finish would not be good. For to clean the mold surface, Frekote 700 N/c solution was used. Extra material from the mould surface was scratched till it became smooth and clean.

Fig. 4 cleaning of mould Fig. 5 Application of Frekote 700 N/c



2.3Applying releasing agent

To remove the final product easily from the mould, release agent (Air Tech 2) was applied on the mould surface. Later a sheet of fine fibre was then used to cover the mould for easy removal of the final seat from the mould surface.

Fig. 6 Application of releasing agent Fig. 7 Application of fine fiber sheet

2.4 Placement of glass fibre fabric and Resin

Glass fibre sheet was cut according to the dimensions of mould. After the cutting was done, it was placed and rolled properly on the same mould. Then for each layer of glass fibres, the resin was prepared by stirring 400g of polyester and styrene with 0.8 g of cobalt well for 1 minute. After the mixing of cobalt, 8g of MEKP was added and again the whole solution was stirred for another 5 minutes. This process was repeated for four glass fabric layers



Fig. 8 Placement of fiber sheet Fig. 9 Application of resin

2.5Application of vacuum

In order to avoid the air entrapments, dry spots and resin rich areas, vacuum was applied. To do the vacuuming, the samples were wrapped using Teflon and then breather material over it. Then vacuum was generated using the suction pump.



Fig. 10 Breather placement Fig. 11 Vacuum application

2.6Curing

The curing of polyester resin takes place at room temperature. So, autoclave was not used throughout the process. And this was observed that only 4-5 hours were required for the complete curing of product.

2.7Attachment of legs with the base

The final and most challenging task was to attach the legs with the base of seat so formed. As bonding is the best way to attach something with the composite. So, In order to accomplish the task, the plastic plate was bonded with the base using the smaller layers of same fabric. After the solidification, the legs were simply screwed with the plate.

Fig. 12 Attachment of plate with base



3 Optical microscope observation

3.1 Microstructure examination:

The mechanical property of any component made out from any composite material depends upon its microstructure. In order to know about the microstructure of the chair, the microstructure examination was done. This experimentation requires various steps to be followed, so that each and every fibre should become visible under the microscope. Also the defects like voids, resin rich and poor areas could be examined and appropriate value for volume fraction of fibre can be calculated.

The steps followed during the examination may consist of sample preparation, grinding, polishing and analysing the specimens.

1. Sample preparation:

A) Firstly, 3 samples of 22.88 mm * 23.96 mm each with the help of diamond cutter were taken out form the unwanted portion of the seat refer fig... The first and third samples were taken out from the straight portion and the second sample was taken out from the curved portion of the seat as shown in fig. 13.

Fig. 13 shows the samples positions



Fig. 14 Preparation of sample Fig. 15 Molds containing solution & samples

B) Secondly, in order to mount the samples in the plastic containers, the solution using Epon Resin 828 and Curing Agent 3046 was prepared. For each 100g Epon resin 828, 45g Cure Agent 3046 should be added. After mixing the solution, the vacuum was applied for 15-20 minutes, so that no air bubbles should be remained in the solution and then the same solution was poured into two moulds, shown in fig. 15. After 24 hrs the solution got solidified and was taken out from moulds. Figure number 16, shows the samples after complete solidification.

Fig. 16 Final samples



2. Grinding and polishing

Fig. 17 Grinding Machine

After preparing the samples, the grinding operation is to be done. The grinding machine upon which different grades of grinding papers were easy to mount and was capable of running at variable speeds was used. Figure 17, shows the grinding machine used to grind the samples. The grinding was done using silicon carbide paper of grade 240, 320, 400, 600, 800, 1200 sequentially. Diamond extender was used as the polishing solution and diamond suspensions (3µm and 1µm) were used for primary polishing and colloidal silica suspension (0.05 µm) was then used for final polishing, refer figure 18. Nylon artic and imperial was used for primary and final polishing. The table no. 1 was referred throughout the process.



Fig. 18 Grinding of samples

Table 1. Grinding and polishing (for Epon 828 with Epicure 3046)

Step Type Surface Grit size Lubrication Pressure(psi)

Load perSpecimen

(lbf)

RotationSpeed(rpm)

Time

0 Grinding SiC Disc 240 Water 15 3 250 30 Sec

1 Grinding SiC Disc 320 Water 10-15 3 250 30 Sec

Repeat Step 1 unil flatness of all samples

2 Grinding SiC Disc 600 Water 7‐10 3 250 30 Sec

3 Fine Grinding

SiC Disc 800 Water 10‐15 3 250 45 Sec

4 Fine Grinding

SiC Disc 800 Water 10‐15 3 250 45 Sec

5 Polishing NylonArtic

3 MicronDiamond

Suspension

Water baseddiamondextender

17‐25 5 150 4 min

6 Polishing NylonArtic

1 MicronDiamond

Suspension

Water baseddiamondextender

17‐25 5 150 4 min

7 Finepolishing

Imperial 0.05 micronSiC

Suspension

Norle 20‐30 6 150 5 min



3. Analysis of specimen

After the preparation of samples, the unpolished side of the specimen was cut to make it straight so that one can analyse those same samples correctly. Now, the specimens were placed under the microscope, the magnification power of the lenses used was increased step by step. At 10X the images were taken out using image analyser software. Fig. 19, shows the microscope used and figure no. 20, 21, 22. shows the images of the samples taken.

Fig. 19 Microscope

Microscopic images of samples



Fig. 20 Fig. 21

Fig. 22



Though, the cross-section of fibres appeared to be somehow elliptical, but the calculations for diameter of fibres were done by taking it to be circular in cross-section. Some voids, resin rich area and dry spots were identified, which eventually lead to lower the strength of the sample. Figure number 20, clearly shows the orientations of fibers in 0 and 90 degrees. The vertical lines show fibers at 0 degrees and the circles shows the fibers at 90 degrees. The dark black portions show the defects in the samples.

3.2 Calculations for fibre volume fraction:

51.9 μm 57.9 μm

Sample 1 sample 3

53 μm

Sample 2

Fig. 23 shows the sections of samples 1, 2, 3 under microscope



In order to calculate the volume fraction of the fibre, the square elements of lengths 51.9, 57.9 & 53 micro meters from the microscope snap shots for sample 1, 3 and 2 are taken into consideration.

For sample 1 square element, the number of fibres in this square element observed as 9 fibres and the diameter of each fibre is calculated to 16 micrometers. Therefore the total area occupied by 9 fibres and area of square element can be calculated and by using the relation for volume fraction, given by:

The value for Volume fraction for fibres can be calculated and comes out to be 66.965%.

For sample 3, diameter of fibre is comes out to be 16.2 micrometers and by using the above relationship; the volume fraction is calculated to 61.5%.

Also, same calculations for sample 2 are performed with diameter of fibre and length of square element taken as 15.47 micrometer, 53 micrometer respectively, the volume fraction of fibres come out to be equal to 60.25%.

4. Cost Analysis:

In order to have a good idea about the expenses of whole project, the costs related to almost all the materials and labour costs per hour were taken into consideration. Table no 2 & 3 show the total cost for materials and Labour costs respectively.



A) Material cost details:

Table no. 2 Total Material Cost

Material used Quantity Unit Cost (CAD$) Total Cost(CAD $)

Woven glass fiber sheet

3.65$ per lb 11

Polyester with styrene

MEKP

Cobalt

Breather 5.9 $ per Yard 2.5

Release Film 0.25 $ per Kg 0.1

Release Agent 14 $ per 100ml 2.8

Legs 10

Sum



B) Labor Cost Detail:

Table no. 3 Total labor cost

Type of work Persons involved Unit Cost(CAD$ /hrs.)

Time taken(Hrs.)

Cost (CAD $)

Preparing materials and cutting

2 10 3 60

Laying up 3 14 3 126

Grinding 2 14 1 28

Inspection(Macroscopic and Microscopic)

1 14 1/2 7

Other cost 20

Sum 241



Appedix

Table no. 4 Materials and equipment used in the whole project

S.no.

Material and equipment

Specification and application Dimension

( if any )

Quantity

1. Mold Plastic chair to give the shape to your chair Fig. 4

1

2. Woven fabric sheet

Glass fiber 4

3. Cleaning agent Frekote 700 N/c 200 gm4. Breather Non woven ultra high temperature breather,

Air wave UHT-800 For proper vacuuming at elevated temperature.

5. Release film Release film 5200 MFG-Airtech, For easy removal from the mould

6. Adhesive tape Yellow, 2 cm wide ,for proper sealing the vacuum bag

1 roll

7. Vacuum plastic bag

Plastic sheet, to create vacuum

8. Vacuum pump Max pressure inlet -150PSIG, Max temperature-125◦F ,product no -3532-1082,To suck the air from the composite

1

9. Cutting Machine Small diamond cutter , too cut the samples 110. Polyester resin

( for Mounting)To make composite and adhesion to the layers and plastic plate

11. oven Fisher, small isotemperature vacuum oven model no-281

1

12. Polishing Machine

To smooth the sample for further test 1

13. Optical digital microscope

To analyse the quality of the composite we prepared for your seat.

1

14 MEKKP For curing process



References

final composites file9

Education

course project

nonmetallic materials

department of mechanical

industrial engineeringreport

main constituents of

liquid composite molding

present project

mechanical property