Consolidation of Self-Reinforcing Composites and Testing of Mechanical Properties.

Transcription

1 Mohammed Khan Matric No: 6486 MSc Project Title: Consolidation of Self-Reinforcing Composites and Testing of Mechanical Properties. Under Dr. Phil Harrison Mechanical Engineering Dept University of Glasgow - -

2 CONTENTS. Abstract.. Introduction to Material. Material Interest, Properties and Recycling Thermal Press and Manufacturer Details Previous Project Overview Thermocouples Calibration Temperature Calibration of Platens Cooling Analysis and Water Flow Rates Temperature between Samples. 8. Pressure Gauge Working and Pressure Calculations 8. Preliminary consolidations 9-. Consolidation of Test Samples. -5. Standards Followed Test Specimens Tensile Testing Results Conclusions Problems Faced & Solutions Acknowledgement 46. References 47. Appendix & 48. Appendix Appendix

3 Abstract Self-Reinforcing Composites referred to SRC are a relatively new class of thermoplastics which contains a high polypropylene core called as polymer and a low melting PP called as co-polymer. The bond between the higher melting polypropylene core and the lower melting copolymer combination the polymers give a large thermal processing window. This combination is done by thermoforming process known as Co-extruded SRC.[] The project is carried out to determine Consolidation process of SRC with time dependent deformation and to investigate Mechanical properties of consolidated material. Availability of machines in our department to consolidate polypropylene woven sheets in to laminates is thermal press, investigate mechanical properties is universal tensile testing machine. The water cooled aluminium platens manufactured and installed to the thermal press which is to be used currently for consolidation of SRC, was done by one of the previous students. These are owned by the mechanical department of the university to drop temperature during the consolidation of SRC. Though the platens were installed, water experiments could not be executed as the O-rings used in between the platens to stop water leakage arrived after the completion of the project by previous student. Reassembled platens to press which were manufactured to be easily fitted. Carried out few experiments, by water flow to check leakages. Leakage was found from nozzle threading which was later fixed using pressure resistant tape (Teflon tape). Platens were adjusted accordingly to achieve even temperatures on the surface. The consolidation of SRC was carried out at different temperatures and pressures by varying number of layers to be consolidated. The press and platens manufactured were to consolidate samples of maximum area 5mm by 5mm. However the samples were changed to mm x mm and 5mm x 5mm to check the dark borders which were due to high pressure. After consolidation of the samples mechanical properties have been analysed by conducting tensile testing. Testing was conducted on tensile testing machine available in the department at crosshead speed of mm/min using ASTM D68 which is technically equivalent to BS ISO 57. Dog bone or dumbbell shaped test specimens have been prepared according to ASTM D68 standards. Finally, the anisotropic properties have been characterized by testing the test specimens in two different angles at degrees and 45 degrees. The results have been analysed at both water cooling and atmospheric cooling procedures. Tensile strength has been calculated and plotted in form of graphs which represents the experimental data. - -

4 Introduction The material department interested in investigation is SRC (self- reinforcing composite) polypropylene. This material is known as new class of thermoplastic composite, which has a fibre and matrix composed of same material. Trade name of this material is Armordon produced by company named Don & Low one of the Scotland s oldest companies and presently one of the leading European manufacturers of Polypropylene based textiles. The composites are mainly classified into two types (i) Co-extruded and (ii) Hot compacted. The one currently working on is Co-extruded polypropylene. Some other polypropylene based material is Curv from Propex Fabrics which is hot-compacted type polypropylene. A co-extruded polypropylene tape consists of distinct layers; lower melting point copolymer PP called as cap or co-polymer coats on each outer surface. This is encapsulated with a high melting PP core called as polymer. The layers are combined during the co-extrusion process, the bond between the higher melting polypropylene core and the lower melting copolymer PP outer cap coat layers is very strong. During subsequent downstream thermal processing the co-polymer melts fusing to polymer fabric together. The higher melting polymer core remains unaffected by the processing heat and retains its excellent properties. The combination of polypropylene polymers with different melting points gives a large thermal processing window. The tapes are highly orientated to give optimum physical properties. Alternatively the tapes are woven into a fabric. Single or multiple layers of this fabric can be thermally consolidated into laminates or panels. [] Curv is manufactured by Propex Fabrics. Extruded polypropylene film is stretched into tapes with exceptionally high stiffness and strength. These tapes are then woven into fabrics and undergo a patented hot compaction process in which the surface of every tape is partially melted, creating a matrix which bonds the tapes into a selfreinforced composite.[] The SRC are expected to retain good mechanical performance which we are currently investigating due to better interfacial bonding between fibre and matrix[ ]. The project is taken for further investigation of SRC mechanical properties after consolidation with time dependent deformation at different temperatures and changing number of layers randomly. The polypropylene sheets provided by Don & Low consists dense and are highly-crystalline. PP refers to polypropylene in this report, PP woven sheets (fibre) coated with thin layer of low-crystalline PP co-polymer, which acts as matrix phase to SRC. To resemble like carbon these sheets have been dyed in black colour. SRC refers to Self Reinforcing Composite fibre which is polymer embedded with an amorphous polymer matrix which is co-polymer, where the matrix material and reinforcing polymer are made up of same monomer units. The co-polymer (matrix) material has low crystalline and a low melting temperature when compared to reinforcing fibres, fibre material has a high crystalline and high melting temperature and is anisotropic. If crystalline level differs, higher melting temperatures are observed for reinforcing fibres. Significantly the matrix material due to low glass - -

5 transition and low crystalline melt at low temperatures surrounding the reinforcing fibres intact and solidify fix making continuous phase between fibres which referred to as first criteria for effective composite performance. Consolidation transforms a flexible SRC fabric into a rigid product. This consolidation requires pressure and temperature for bonding of matrix material []. Material Interest SRC materials are expected to have good mechanical properties due to interfacial bonding between fibre and matrix [4]. The matrix holds fibre together even though fibres are strong they can be brittle under stress conditions. In simple words matrix adds toughness to composite. Fibres have good tensile strength however the disadvantage is they have low compression strength. Matrix provides additional compression strength to the composite. Fibres are of interest even though they have good and bad points. One of the main reasons is they contain glass in most popular fibre which are really cheap. The glass content in fibres is spun into tiny fibres due to which they are really strong and flexible [5-6]. The other point of interest in fibres is they are recyclable without any issues hence cost effective. Material Properties SRC have good chemical and mechanical properties. Most commercial polypropylene has an intermediate crystalline between low density polyethylene and high density polyethylene. Due to which it is less flexible than low density polyethylene and less brittle than high density polyethylene. This property is the main reason for replacement of engineering plastics with polypropylene i.e.; SRC material. Polypropylenes have a very good resistance to fatigue due to which most of the fliptop bottles. Due to good dielectric properties this material is used with high performance pulse and low current loss capacitors [7]. Polypropylene has a melting point of 65 degrees due to this characteristic property many medical and laboratory items are made with this material[7]. Applications Polypropylene is a thermoplastic polymer made by chemical and textile industries, which are used in vast applications like food packaging, ropes, textiles and plastic parts, reusable containers of various type, laboratory equipments, loudspeakers, automotive components, and polymer bank notes. They are used as insulation for electrical cables in low ventilation environment preliminary tunnels. The companies that are normally involved in the manufacturing of polypropylene material take this phenomenon into consideration [8]. Major applications after investigations and research on mechanical properties will be used in automotive fields specially for interior and under hood applications like head liners as thin as mm to offer increased heat impact protection and maximise noise abatement. Another application after doing ballistics testing on this material is to implement this product as bullet proof jackets for military purpose [9]

6 Recycling The major issue for any material or product in current life is recycling. Polypropylene is easy for recycling. The companies that are normally involved in the manufacturing of polypropylene material take this phenomenon into consideration. Recycled polypropylene can be used for packing containers and recycled fibres can be used into new products. On one hand mechanical recycling is considered as the best recovery option for large polypropylene automotive components, on the other hand, energy recovery is solution for most small plastic parts. Blending of recycled polymers may help to improve properties of materials. Recycled polymers may vary in compositions and poor properties but additives can be used to improve properties. Recycling of polymers is beyond any doubt in this industry will be looking for environmentally friendly and cost effective alternative []. Thermal Press The thermal press currently working on for consolidation of SRC is a hydraulic thermal press; source for heating up the press is electricity. Model of thermal press is S6/95. Fig Thermal Press

7 Thermal press manufacturer is Mackey Bowley International shown in Fig who is one of the UK s companies known as specialist in designing and manufacturers of custom built hydraulic presses for major industries in both new and used/rebuilt hydraulic presses. They also manufacture guillotines for polymer industries. They manufacture vast range of presses like -Extrusion Presses -Composite Presses -Multi Station Moulding Presses etc.; Contact Details: Mackey Bowley International Gravesend, Kent. DA PT UK Phone: Website: Previous Project Overview Project was undertaken by a student named Andrew Cochrane to design, manufacture and installation of water cooled platens to the thermal press. Aim of this project was to provide active cooling to SRC during consolidation. Thermal press cools down very slow after the heater turned off by convection and radiation of surrounding atmosphere. The press contains 4 heaters in upper and lower moulds 8 in total. As shown in Fig. this provides required temperature. Fig Heaters inside Thermal Press Mould. The implementation of water cooled platens will allow rapid temperature drop in a controlled manner. The material selected for these platens is Aluminium. The platens are designed to have even temperature on surface as much as possible. To acquire this platens are manufactured having two channels which contains one inlet and one outlet to each channels. Reason for these channels is to introduce water with same flow rate in opposite directions at same time, which will result in more even temperature distribution than water flowing through both channels in same direction. Also the inlet was designed lower than outlet intended to reduce trapping of air inside platens during water flow. As shown in Fig, the platens have rounded corner channels which will drop the water pressure

8 Fig Aluminium Platens. The platens are manufactured as a pair one for upper and other for bottom half of the thermal press. Each half is sub manufactured in two halves which is assembled by screws this is done to provide an O-ring between them to avoid water leakage during water flow. The overall dimensions of the platens are 5 x 5 mm equivalent to the press plates. size of 5 x 5 mm sample can be consolidated on these platens. The platens were simulated using Finite Element Analysis software, temperature distribution was also analysed at both steady and transient conditions. The consolidation of SRC has been conducted but did not conduct any experiments using water flow through platens as the O-rings did not arrive in time. The press shown in Fig 4 is after assembling of platens along with nozzles and heat resistant pipes. Fig 4 Thermal Press after assembling of platens

9 Disassembled and reassembled platens to press using O-rings between platens before starting the current project. Thermocouples Calibration To conduct temperature calibration over the platen surface thought of calibrating the thermocouples to check if there is any error before moving further. This has been done using boiled water and glass thermometer. The available numbers of thermocouples were 6 but realised one was not working so ignored that and calibrated remaining 5. Boiled the water to degrees as recorded on the thermometer then introduced the thermocouples in the hot water and recorded temperature for every degrees in a decrement order, refer Appendix for readings, but plotted in ascending order in graph for easy understanding. According to the Figure 5 below there was not much difference in thermocouples when compared to thermometer, thinking which is negligible. Temp ( C) Thermocouples calibration using glass thermometer Thermometer Probe Probe Probe Probe 4 Probe Seies of thermocouples Fig 5 Thermocouples Calibration with glass thermometer. The surface temperature is been tested using the calibrated thermocouples. Set temperature is referred to dial temperature of press in this report. Set temperature to 6 degrees and recorded the reading on surface of platens by placing the thermocouples at different positions and also at a single position. Recorded temperature of thermocouples at a fixed position by placing two thermocouples at same time is shown in Table below Position Top-- -Platen Bottom-- -Platen Probe Probe Probe Probe 4 Centre Corner Table Probe readings at set temperature. The readings were recorded as soon as the set temperature reached to 6 degrees left it for 5 minutes to record the actual temperature. As shown in Table the actual temperature recorded - 8 -

10 Position Top-- -Platen Bottom-- -Platen Probe Probe Probe Probe 4 Centre Corner Table Probes reading actual temperature at different positions. This shows that the average temperature along the surface of top and bottom platens at set temperature is 55 degrees. The temperature was checked by interchanging the probes on platens simultaneously, recorded the same. This confirms that the thermocouples were working fine so have used the same thermocouples further. Temperature Calibration of Platens (Heating) Platen temperature was calibrated to find actual temperature on surface at different set temperatures. Set temperature is referred to dial temperature of press as shown in Fig 6, internal probe is the temperature read by dial during heating. Set temperature to 5 degrees on dial time taken to reach this temperature is recorded as min and sec, where no thermocouples have been used during this because set temperature shows up on dial of press. Top Platen Bottom Platen Internal Probe Set Temperature Fig 6 Dial of thermal press. When the set temperature has reached 5 degrees placed the thermocouples and recorded the temperature at different positioning on platen surface. Refer Fig 7 for thermocouple positions. Fig 7 Positions of thermocouples

11 Temperature recorded on the platens surface at this time was Top platen 4.5 degrees and Bottom platen was 4.5 degrees, there was a difference of one degree between both platens may be due to heaters or convection. The platens were left for 5- min to record the actual temperature at this set temperature. Recorded temperature after this time was top platen 47 degrees and bottom platen 46 degrees; this is the actual temperature after which the temperature was constant. Plotted a graph for easy understanding, refer to Fig 8. The overall temperature difference between two platens is degree considering it to be acceptable. The calibration is done at various different temperatures to figure out the actual temperature. Temperature calibration of 5 o C set on dial Top Bottom Temp ( o C) Time in min Fig 8 Temperature calibration@5 C Set temperature 7 C Time taken to reach from 5 C is 9 min. +9 = 9min Actual temperature, top platen 67.5 C and bottom platen 66.5 C Refer Fig 9. Temperature calibration of 7 o C set on dial TOP BOTTOM 68 Temp ( C) Time (min) Fig 9 Temperature C - -

12 Set temperature 9 C Time to reach from 7 C is 9 min = 8min. Actual temperature, top platen 86.5 C and bottom platen 85.5 C Refer Fig. Temperature Calibration of 9 o C set on dial TOP BOTTOM Temp ( C) Time (min) Fig Temperature 9 C Set temperature C Time taken to reach from 9 C is 4 min = 4 min Actual temperature, top platen 6.5 C and bottom 4.5 C Refer Fig. Temperature Calibration of o C set on dial TOP BOTTOM Temp ( C) Time (min) Fig Temperature C - -

13 Set temperature 5 C Time taken to reach from C 5 min = 57min Actual temperature, top platen 45.5 C and bottom platen 4.5 C Refer Fig. Temperature Calibration of 5 o C set on dial TOP BOTTOM Temp ( C) Time (min) 4.5 Fig Temperature C Set temperature 7 C Time taken to reach from 5 C is min = 69min Actual temperature, top platen 64.5 C and bottom platen is 6.5 C Refer to Fig. Temperature Calibration of 7 o C set on dial TOP BOTTOM Temp ( C) Time (min) Fig Temperature 7 C - -

14 Calibration tests conducted at different temperatures observed that time taken to reach actual temperature after reaching set temperature is approximately 5min. Noticed temperature difference before degrees is noted to be degree between top and bottom platens after degrees has increased to degree, this might be due to heat loss around the platens or might be due to heaters or heat convection. Further tests are required using thermal insulation around the platens to make sure why is it happening so. Empirical formula for Actual Temperatures Equation has been derived to calculate the actual temperature at any set temperature, the equation is in form of y = m x + c, where m and c are constant x is set temperature. Refer to Fig 4 for temperature differences between Top and Bottom platens. For top platen it is y =.7 x Accuracy is.99 % For bottom platen it is y =.9 x Accuracy is.99 % Equation for Actual Temp TOP BOTTOM Linear (TOP) Linear (BOTTOM) SET TEMP ( C) y =.9x R = y =.7x R = ACTUAL TEMP ( C) Fig 4 Empirical formulae for actual temperature. After temperature calibration of platens was easy to figure out the actual temperature at any set temperature. - -

15 Cooling Analysis of Platens Cooling analysis of platens was carried out to study the cooling behaviour. Cooling analysis of platens was done at a fixed set temperature 5 C, but cooled by different sources. The three main sources easily available were water flow cooling, compressed air flow cooling and atmospheric cooling. (i) Water cooling process Water cooling process was done at set temperature 5 C after reaching actual temperature which was 44.5 C at an average of top and bottom platens. Before doing this the water flow rate from tap, inlet and outlet nozzles was measured. All the flow rates were measured using a 5 ml glass beaker. Refer to Fig 5. Fig 5 Measuring water flow using glass beaker. The water flow rate from tap has been measured Refer Appendix for flow rate readings. Refer Fig 6 for flow rate from tap. measurement(ml) Flow rate measure from Tap y = 6.55x R = Left(Top) Right(Bottom) Linear (Left(Top)) Linear (Right(Bottom)).84 y = 5.9x -.57 R = Time(sec) Fig 6 Water flow rate from tap

16 Water flow from left tap is supplied as inlet to top platen and right to the bottom. Using the empirical formula from Fig 6 the water flow rate can be calculated. y = 6.5 x 8.8 Accuracy = 99% x is volume of water in ml. Water flow rate for Bottom platen can be calculated by using formula y = 5.9 x.5 Accuracy = 99% Refer to Fig 7 for water flow rate for inlet and outlet of platens and Appendix for water flow readings from tap, inlets and outlets. 6 Water input to platens Top Bottom Water measurement (ml) 5 4 y = 7.555x + 7. R =.997 y = 8.67x R = Time (sec) Fig 7 Water flow rate to inlet of platens (Top and Bottom). Water flow rate at inlet to both top and bottom platens were measured and flow rate for top platen can be calculated by using the empirical formula Similarly for bottom platen y = 7.555x + 7. Accuracy = 99% y = 8.67x Accuracy = % Water flow rate for outlet of the platens both top and bottom was measured using the same 5ml glass beaker. Refer to Fig

17 Water output from platens Top Bottom 6 Measurement (ml) 5 4 y = 7.5x R =.998 y = 7.79x R = Time (sec) Fig 8 Water output from platens (Top and Bottom). Water flow rate at outlet of top platen can be measured by using the empirical formula y = 7.79x Accuracy = 99% Similarly for bottom platen y = 7.5x Accuracy= 99% Noticed that the water flow from the bottom platen is very high at out let when compared to inlet this might be due to the bottom platen being lower than the top platen. After measuring the flow rates the water was passed through the platens after the platens reached actual temperature. Noticed that there was only steam coming out till there is a temperature drop of 5 degrees from 5- degrees, after which there was a continuous flow, time taken to get the temperature down from 5 degrees that is room temperature is 7min refer to Fig 9 for temperature drop and empirical relation. The empirical has been found to calculate time for temperature drop during water cooling process is y = x + 4. Accuracy = 99% (ii) Compressed air cooling process After water cooling used compressed air to make sure no water left in platens, and then set temperature back to 5 C to conduct compressed air cooling. Time taken to reach this temperature was 57min due to very less quantity of water left in platens which did not make big difference reaching the set temperature, observed steam coming out at temperature - degrees. Recorded actual temperature which was 44.5 C on an average of top and bottom platens, where top platen was 45.5 C and bottom platen was 4.5 C. Then using low HP air compressor the compressed air - 6 -

18 has been passed through inlets of both top and bottom at a constant pressure, the outlets were left open in atmosphere. Recorded time to drop temperature from 5 C to room temperature that is degrees took mins refer to Fig 9 for temperature drop and empirical relation. The empirical has been found to calculate time for temperature drop during compressed air cooling process is y = -.48 x Accuracy = 99% (iii) Atmospheric cooling process To conduct atmospheric cooling raised set temperature back to 5 C. Recorded actual temperature to be same as before. The platens were left open to cool down at room atmosphere and convection. Recorded time taken to reach room temperature from 5 C was 6min. Refer to Fig 9 for temperature drop and empirical relation. The empirical relation has been found to calculate time for temperature drop at atmospheric cooling process is y = -.96 x Accuracy = 99% Temperature Cooling Measurement of Platens AIR ATM WATER Linear (AIR) Linear (ATM) Linear (WATER) Temp (C) y = -.48x R =.9986 y = -.96x R =.999 y = -.469x + 4. R = Time (min) Fig 9 Cooling rates of platens at water, compressed air and atmospheric. After conducting tests for temperature drop noticed that there was faster drop in temperature by using water flow than compressed air and atmospheric cooling. The compressed air cooling process was almost similar to atmospheric cooling, hence decided to consolidate samples using water cooling and atmospheric cooling for further investigation of mechanical properties in fast cooling and slow cooling

19 Temperature Calibration of Sample (Heating) After study of cooling rates a sample has been pressed within the thermal press at 5 C set temperature to check temperature between layers of SRC regardless of consolidation and applied a very less pressure of around bars. Placed two thermocouples after 7 layers of SRC while the sample was of 5 layers. The sample was placed within the press after reaching the actual temperature which was 45 C, after - minutes the sample was removed as the insulation of thermocouples was burning and noticed that the sample was trying to consolidate along with the thermocouples. Recorded temperature before removing the sample was 44.5 C on an average, as one of the thermocouple was reading 44 C and the other 45 C which was almost equal to the actual temperature. Pressure Gauge Working and Calculations Thermal press contains a pressure gauge which reads the pressure of fluid acting on the piston, as the piston moves in upward direction. The pressure on sample varies as the area of platens is different. As shown in Fig the pressure gauge reads two types of units:. Pressure in Bars. pressure in Psi Fig Pressure gauge of thermal press. Preferred pressure in bar in this project. When the pressure is set to bar the pressure acting on the sample is calculated as: Diameter of piston for current press model is = 54. mm Area piston = /4 d = /4 (.54) =.86 m Area Sample = 5 x 5 mm =.5 x.5 =.65 m - 8 -

20 Pressure on sample = pressure of piston x Area piston / Area Sample Pressure of piston = bar = x 5 N/ m P sample = x.86 /.65 = 9.76 bar bar Using these calculations we can find the actual pressure acting on sample during consolidation. Preliminary Consolidation Experiments After study of cooling rates and temperature between samples as a trial a sample has been consolidated at set temperature 55 C. The sample size is 4 x 4 mm, 4 layers of SRC at a pressure of bars on gauge. Time taken to reach set temperature is 56 min and left for 5 min to reach actual temperature the placed 4 layers of SRC in side the press and applied pressure of bar and left sample inside the press for 5 min for consolidation at same temperature and then turned off set temperature and left the sample to cool down at room atmosphere. Refer to Fig. Observed consolidation was good, but observed dark boundary along the borders of sample, refer to Fig was not able to figure out was it due to heaters or due to high 55 ( C) set,act 5 ( C), 4 x 4 mm,4 lyr At/C Placed Sample Temp ( C) Time (min) Fig 55 C set, Act 5 C, Atmospheric cooled

21 Fig Sample after consolidation at 55 C set temperature. Repeated the experiment again at same conditions, but changing the pressure by 5 bars on gauge instead of bars. Observed the sample to be same as before, which concludes that this is happening at all pressures. Further investigation is needed to figure out why it is happening. Conducted a few consolidation experiments, varying the sample size and water cooled process. Previously samples were consolidated with area of 4 x 4mm changed the size to x mm and 5 x 5mm. Sample size: x mm Set temperature 5 C Actual temperature 47 C Pressure bar Sample left in mould min. Water cooled Refer 5 ( C) set temp,act 47 ( C), 4 lyr, x mm W/C Placed Sample Temp ( C) Time (min) Fig 5 C set, Actual 47 C, Water cooled. - -

22 Sample size: 5 x 5mm Set temperature 5 C Actual temperature 47 C Pressure bar Sample left in mould 5min Refer Fig 55 ( C) set, Act 5 ( C), 5 lyr 5 x 5mm W/C Placed sample Temp ( C) Time (min) Fig 4 55 C set, Actual 5 C, Water cooled. The boundaries along the borders of sample were noticed again, which indicates that there was high pressure acting along the borders of sample. This was due to bowing effect in the platens at the pressures applied refer Fig 5. Platen Pressure acting on sample Sample Fig 5 Bowing effect of platen at high pressure on sample. Tried using aluminium foils on both sides of sample to check if this makes any changes, placed aluminium foil below and above of sample equal to sample size. Refer Fig

23 @55 ( C) set,act 5 ( C), 4 x 4mm, 4lyr. W/C Placed Sample Temp ( C) Time (min) Fig 6 Consolidation of sample with aluminium 5 C set, Water cooled. This test did not make any much difference, but in fact given a good surface finish on the sample. Tried the same test by using 4 layers of aluminium foils in middle of sample of area x mm, where the sample size was 4 x 4 mm. Refer Fig 6, as the procedure and temperature was same. This trial also did not make difference but it gave dark boundaries along the boundary where the aluminium foil was placed and also along the borders of the sample area. Tried a sample by removing the platens to check if any problem with platens, but noticed the same kind of dark boundaries along the borders. This makes thinking of bowing effect of the press. Reassembled the platens and consolidated a sample by placing sample diagonally to the platens to check if this makes any change. Refer Fig 6 as it was on same conditions. The sample was much better than before in spite of leaving dark boundaries along the surface it was only at 4 corners of sample. Refer Fig 7 for sample after consolidation in diagonal position. Dark Boundaries. Fig 7 Sample consolidated diagonally in press. - -

24 The use of aluminium foils did not resolve the problem, but consolidating the samples diagonally gave better result than before so decided to consolidate test samples following this procedure. Concluding that this problem was due to bowing of platens at high pressure, due to which the pressure was acting along the borders of the sample. Further simulation of platens is required to solve this problem. Consolidation of Test Samples Consolidated test samples at 4 different temperatures 4, 47, 5 and 5 degrees. From here on all the temperatures taken are referred to Actual temperatures. The set temperatures for these temperatures are 45, 5, 55 and 58 degrees. These specific temperatures have been selected to investigate Tensile strength and mechanical properties according to Korean science and engineering foundation paper. To get the samples at same test conditions consolidated three set of samples at each test conditions separating them by placing aluminium foils in between. Each sample is of size 4 x 4 mm and 4 layers, sample before and after consolidation as shown in Fig 8 placed the samples in press in diagonally along with an aluminium strip to cut test specimens for T-peel testing. Samples bottom, middle and top Aluminium strip Fig 8 Consolidation of samples at same test conditions for tensile strength and T-peel testing. Test samples were consolidated at both fast cooling and slow cooling conditions at different processing temperatures. Sample size 4 x 4 mm Set temperature 45 C Actual temperature 4 C Pressure on gauge bar Pressure on sample bar Atmospheric and water cooled Refer Fig 9 - -

25 @45 ( C) set, Act 4 ( C) W/C At/C Placed Sample Temp ( C) Time (min) Fig 9 consolidation of test 45 C set, W/C and At/C Sample size 4 x 4 mm Set temperature 5 C Actual temperature 47 C Pressure on gauge bar Pressure on sample bar Atmospheric and water cooled Refer Fig Temp ( C) ( C) set,act 47 ( C) W/C At/C Place Sample Time (min) Fig consolidation of sample at 5 C set, W/C and At/C Sample size 4 x 4 mm Set temperature 55 C Actual temperature 5 C Pressure on gauge bar Pressure on sample bar Atmospheric and water cooled Refer Fig - 4 -

26 Temp ( C) ( C) set, Act 5 ( C) W/C At/C Placed Sample Time (mm) Fig consolidation of sample at 55 C set, W/C and At/C Sample size 4 x 4 mm Set temperature 58 C Actual temperature 5 C Pressure on gauge bar Pressure on sample bar Atmospheric and water cooled Refer Fig Temp ( C) ( C) set,act 5 ( C) W/C At/C Placed Sample Time (min) Fig consolidation of sample at 58 C, W/C and At/C For all temperature readings refer Appendix. Standards Followed ASTM D68 was the standard followed previously by Korean science and engineering foundation to investigate mechanical properties of laminated SRC, and - 5 -

27 tensile strength was calculated. Preferred ASTM D68 standard again to maintain the same standards and investigate if any changes in mechanical properties by using water cooled platens. This standard is generally used for materials whose thickness is less than mm up to 4mm. according to this standard thin film less than mm test method D88 is preferred test method, but according to D88 thin films have been arbitrarily defined as sheeting having nominal thickness not greater than.5mm. The thickness of consolidated samples is measured to be.48mm which is greater as defined in D88. So has preferred to go with ASTM D68 standard, which is also technically equivalent to ISO 57. Significance and Use The test method is designed to produce tensile property data for the control and specification of plastic materials. For any material, there will be a specification that requires the use of test method for research and development purpose. Tensile properties may vary with specimen preparation and with speed and environment of testing. Apparatus A testing machine of the constant rate- of-crosshead-movement type and comprising is used as shown in Fig.This contains Fig Universal tensile testing machine

28 -A fixed or essentially stationary member carrying one grip. -A movable member carrying a second grip. -Grips for holding the test specimen between the fixed member and the movable member of the testing machine preferable self-aligning type. -Self-aligning grips are attached to the fixed and movable members of the testing machine in such a manner that they will move freely into alignment as soon as any load is applied. -A load-indicating mechanism capable of showing the total tensile load carried by the test specimen when held by the grips. -An extension indicating mechanism capable of showing the amount of change in the separation of the grips, that is, crosshead movement. -Inbuilt extensometer to read the extension of specimen when load applied. Test Specimens According to ASTM D68 the test specimens are classified in to V types depending on their thickness. Thickness of current consolidated SRC is.48 which is less than mm and as per the standard it falls in type V. Refer to Fig 4 the specimens are cut into dumbbell shaped for tensile testing also called as dog-bone shaped. Fig 4 Test specimen as per standard. Dimensions of type V test specimens thickness less than mm are in Table below. Dimensions Type V less than mm (mm) W-Width of narrow section.8 L-Length of narrow section 9.5 WO- Width overall 9.5 LO-Length overall 6.5 G-Gauge Length 7.6 D-Distance between Grips 5.4 Table : Dimensions of test specimen. Number of specimens per sample according to standards is 5 at same test conditions. Number of samples cut per sample is and number of samples prepared at same test conditions is. Total number of specimens is 9 in total at same test conditions. To characterize the anisotropic properties the test samples at two directions ( and 45 degree angles). As shown in Fig 5. All the specimens were managed to cut by using scissors maintaining the tolerances

29 Specimen Specimen Specimen Fig 5 Test samples cut off from sample at and 45 degrees. Speed of Testing according to standard for Type V specimens is shown in Table 4 below. Classification Speed in mm Type V Table 4: Cross head speeds for tensile testing. Speed followed is mm per min, Conditioning of test samples according to the standards is ± C, so conducted all the testing at room temperature which was C. Testing Procedure -Measured the width and thickness of each specimen to the nearest.5 mm using the current standard. -Measured the width and thickness of flat specimens at the centre of each specimen and within 5 mm of each end of the gauge length. -Placed the specimen in the grips of the testing machine, taking care to align the long axis of the specimen and the grips with an imaginary line joining the points of attachment of the grips to the machine. -The test samples were pulled at 9 degrees along fixed axis. - The test specimens have been pulled till the yield point and recorded the extension of specimen and maximum load applied. The test specimens before and after break are shown in Fig

30 Specimens before testing Specimens after testing Fig 6 Test specimens before and after testing. -Number of test specimens for each sample tested is at degrees angle and for 45 degrees angle and at both water cooled and atmospheric cooled. - Results are plotted as shown in Fig 5, which are for all three samples top, middle and 4 C and degrees angle Atmospheric cooled showing the maximum load before Tensile Strength calculations. Positions of test specimens are taken are mentioned in Table 5 refer to Figure 5 for positions. Specimens Position Middle Between middle and corner Corner edge Table 5 Positions of specimens and numbering. The tensile tested specimen data is collected and according to that data the graphs are plotted to show the maximum load applied on each specimen for every sample at each processing temperature. Refer to Fig 7 for load on specimens, and for the top sample at 4 C atmospheric cooled top a/c degrees Fig 7 4 C, atmospheric cooling at degrees angle for top sample

31 Following the same procedure plotted graph for middle sample for all specimens at 4 C processing temperature atmospheric cooled process. Refer Fig middle a/c deg Fig 4 C middle sample At/C at degrees angle. Similarly plotted graph for all specimens for bottom sample at 4 C processing temperature atmospheric cooled process. Refer Fig bottom a/c deg Fig 4 C, bottom sample a/c at degrees angle. Refer Appendix 4 for graphs showing maximum load for remaining samples. Tensile strength result calculations Tensile Strength = Max / Average cross sectional area of specimen - Max load is referred to L - Cross-sectional area of specimen to A = thickness x width =.48 x.5 =.68 mm - -

32 - Tensile strength is referred to T.S Calculating the Tensile Strength At degrees angle and Atmospheric cooled samples: degrees a/c, degrees angle bottom sample: Specimen. T.S = L / A = /.68 (mm ) = 45.8 MPa (Note: As the result should be in MPa, N/ mm is converted into N/ m ) Specimen. T.S = L/A = 68.6 /.68 = 45.9 MPa Specimen. T.S = L/A = /.68 = 5.7 MPa degrees, middle sample: Specimen. T.S = L/A = /.68 = 77.8 MPa Specimen. T.S = L/A = 64.6 /.68 = 8.9 MPa Specimen. T.S = L/A = 6.78 /.68 = 65. MPa 4 degrees Top sample: Specimen. T.S = L/A = /.68 = 5. MPa Specimen. T.S = L/A = /.68 = 7.8 MPa Specimen. T.S = L/A = / = 9.4 MPa - -

33 Taking average of all 9 specimens for all top, middle and bottom samples plotted as a th point calculating the Standard error. Refer to Fig 4 ( C) degrees angle At/C Specimens Avg T.S (MPa) Specimens Fig 4 Tensile strength of 4 C, degrees angle At/C. Following the same procedure plotted the graph at same processing temperature 4 C actual at degrees position for water cooled process. The th specimen in graph is showing the average of all test specimens. The graph plotted along with standard error. Refer Fig 4. T.S (MPa) ( C) degrees angle W/C Specimens Avg Specimens Fig 4 Tensile strength of 4 C, degrees angle 47 C Actual temperature degrees angle Atmospheric cooled Refer Fig 4 - -

34 T.S (MPa) ( C) degrees angle At/C Specimens Avg Specimens Fig 4 Tensile strength of 47 C, degrees angle 47 C Actual temperature degrees angle Water cooled Refer Fig 47 ( C) degrees angle W/C Specimens Avg T.S (MPa) Specimens Fig 4 Tensile strength of 47 C, degrees angle 5 C Actual temperature degrees angle Atmospheric cooled Refer Fig

35 T.S (MPa) ( C) degrees angle At/C Specimens Avg Specimens Fig 44 Tensile strength of 5 C, degrees angle 5 C Actual temperature degrees angle Water cooled Refer Fig 45 T.S (MPa) ( C) degrees angle W/C Specimens Avg Specimens Fig 45 Tensile strength of 5 C, degrees angle 5 C Actual temperature degrees angle Atmospheric cooled Refer Fig

36 T.S (MPa) ( C) degrees angle At/C Specimens Avg Specimens Fig 46 Tensile strength of 5 C, degrees angle 5 C Actual temperature degrees angle Water cooled Refer Fig 5 ( C) degrees angle W/C Specimens Avg T.S (MPa) Specimens Fig 47 Tensile strength of C, degrees angle W/C Taking the th specimen from all test conditions Graph is plotted using the standard error to show the Tensile Strength at each processing temperature. Refer Fig 48 for degrees angle position for Atmospheric cooling

37 @ degrees angle A/C At/C 45 4 T.S (MPa) Temp ( C) Fig 48 T.S for all processing temperature at degrees angle At/ C. Following the same procedure plotted graph for Water cooled process. Refer Fig degrees angle W/C W/C 45 4 T.S (MPa) Temp ( C) Fig 49 T.S for all processing temperatures at degrees angle W/C. Graph has been plotted to check the difference between Atmospheric cooling and Water cooled process at all processing temperatures at degrees angle. Refer Fig

38 Degrees angle A/C & W/C A/C W/C 45 4 T.S (MPa) Temp ( C) Fig 5 Tensile Strength at all processing temperatures degrees angle both At/C & W/C. Tensile strength for Water cooled process is not making much difference at different processing temperatures at degrees angle position test specimens from samples except at 47 C. To figure out the tensile strength at 45 degrees position the graphs have been plotted following the same 4 C Actual temperature 45 degrees angle Atmospheric cooled Refer Fig 4 ( C) 45 degrees angle At/C Specimens Avg T.S (MPa) Specimens Fig 5 T.S for all test specimens at 4 C processing temperature at 45 degrees angle on sample 4 C Actual temperature 45 degrees angle Water cooled Refer Fig 5-7 -

39 @4 ( C) 45 degrees angle W/C Specimens Avg T.S (MPa) Specimens Fig 5 T.S for specimens at 4 C processing temperature, 45 degrees angle 47 C Actual temperature 45 degrees angle Atmospheric cooled Refer Fig 47 ( C) 45 degrees angle At/C Specimens Avg T.S (MPa) Specimens Fig 5 T.S for specimens at 47 C processing temperature 45 degrees angle 47 C Actual temperature 45 degrees angle Water cooled Refer Fig

40 @ 47 ( C) 45 degrees angle W/C Specimens Avg T.S (MPa) Specimens Fig 54 T.S for specimens at 47 C processing temperature 45 degrees angle 5 C Actual temperature 45 degrees angle Atmospheric cooled Refer Fig 5 ( C) 45 degrees angle At/C Specimens Avg T.S (MPa) Specimens Fig 55 T.S for specimens at 5 C processing temperature 45 degrees angle 5 C Actual temperature 45 degrees angle Water cooled Refer Fig

41 T.S (MPa) ( C) 45 degrees angle W/C Specimens Specimens Avg Fig 56 T.S for specimens at 5 C processing temperature 45 degrees angle 5 C Actual temperature 45 degrees angle Atmospheric cooled Refer Fig 5 ( C) 45 degrees angle At/C Specimens Avg T.S (MPa) Specimens Fig 57 T.S for specimens at 5 C processing temperature 45 degrees angle 5 C Actual temperature 45 degrees angle Water cooled Refer Fig

42 @ 5 ( C) 45 degrees angle W/C Specimens Avg T.S (MPa) Specimens Fig 58 T.S for specimens at 5 C processing temperature 45 degrees angle W/C Using th specimen which is average of all specimens at processing temperatures, along with the standard error plotted graph indicating tensile strength at different processing temperatures. Refer Fig degrees angle At/C At/C T.S (MPa) Temp ( C) Fig 59 T.S for all processing temperature at 45 degrees angle At/ C Following the same process plotted graph for water cooled samples. Refer Fig 6-4 -

43 45 degrees position W/C W/C T.S (MPa) Temp (C) Fig 6 T.S for all processing temperatures at 45 degrees angle W/C To analyse the difference between atmospheric cooling and water cooling plotted results on same graph for all processing temperatures. Refer Fig degrees position A/C & W/C A/C W/C T.S (MPa) Temp (C) Fig 6 T.S for all processing temperatures for 45 degrees angle for both At/C & W/C. The tensile strength is seen to be high in water cooled samples when compared to atmospheric cooled samples except at 5 C processing temperature. T-peel strength results from same test sample at same processing temperature from VIkram Karnam report who was working on investigation of T-peel strength. Refer Fig

44 T-peel strength (N/mm) T-peel strength comparision between Water cooled & Atmospheric cooled specimens Water cooled.5 Atm cooled Temperature (oc) Fig 6 T-peel strength at different processing temperatures

45 Conclusions - Aluminium platens made a difference in saving time during consolidation and also good temperature distribution over the surface. However need further simulation to resolve the problem of bowing when high pressure applied - As the processing temperatures were increased, tensile strength decreased in both atmospheric and water cooling process at degrees. No much difference in tensile strength except resulting high tensile strength at 5 C during water cooled. - High tensile strength for water cooled samples when compared to atmospheric cooled at 45 degrees angle except at 5 C. This might be due to good bonding between matrix-matrix of SRC during consolidation in very less time at water cooled process. - High peel strength at all processing temperatures for water cooled samples when compared to atmospheric cooling process. - According to results this indicates that there is a good improvement in properties of SRC with water cooling process resulting with high tensile strength at 45 degrees angle and high T-peel strengths. - Finally concluded that water cooled process can be used in future for good results and improved mechanical properties of SRC

46 Problems faced during consolidation and future work - Noticed that the water pipes were blowing off due to hot steam during water cooling consolidations. So replaced the water pipes with heat resistant pipes available in department and recovered this problem currently, but has to be changed by good thermal resistant pipes to fix this problem permanently. - Time taking for water cooling was also a bit long so advisable to replace the inlet and out let nozzles with bigger diameter to increase the water flow rate resulting in less time to cool the platens. - Insulation to the platens is also advisable to reduce heat loss from surrounding of platens which will reduce time to reach set temperature and also in good consolidation results during atmospheric cooling process. - Noticed dark boundaries at the edges of the samples after consolidation, this was a major issue to figure out why it was happening discussed this issue with advisor, and been advised may be due to bowing effect in the platens at the pressure applied and heating conditions. Refer to Fig 5 for bowing effect. To overcome this problem further simulation is required to the platens