Purpose:

The purpose of the lab was to check the ability of three different samples to stretch to find the elastic region, elastic limit, plastic region, and fractured limit. These properties help many scientists in determining whether the object is brittle or ductile.

Objective:

The purpose of this lab was to measure and compare the tensile properties of three different samples [Acrylic, Nylon and Polycarbonate (Lexan)] with the help of an UTS tester {Appendix 1} which can apply a maximum force of 20 KN on samples. These properties will help one to get the calculations such as Young’s Modulus, toughness, and yield stress of the three samples

Summary:

After doing the tests, it was noticed that the time taken to break the acrylic sample was least, Lexan second least and nylon the most. These timings may show the properties like ductility and hardness of the three samples.

Theory:

The UTS tester is used to measure various properties of a sample like Elastic Region, Elastic limit, Plastic Region, and the Plastic {Appendix 2}; these regions are sketched on a stress –strain {Appendix 3} graph whose slope itself is the modulus of Elasticity or Young’s Modulus. The formula for Young’s Modulus (E) was derived with the help of Hooke’s law:

Elastic region (or deformation) is non-permanent when the material is returned to original shape after the applied load is removed. According to the textbook Material Science and Engineering by William D. Callister (2011) and David G. RethWisch (2011), the elastic deformation is a type of deformation in which stress and strain are proportional to each other (156).While, when the force applied to the material in such a way that it cannot return to its original shape after removing the applied force, the elastic limit of the material is reached (Croucher 3-3).

After the elastic limit, the “stress is no longer proportional to strain and permanent, non-recoverable, or plastic deformation (region) occurs” [Callister and RethWisch 162]. . According to the textbook “Material Science and Engineering” by William D. Callister (2011) and David G. RethWisch (2011) from an atomic perspective, the atoms breaks it bond with their neighbours to attach themselves to other atoms as they all move around relative to one another (162). Most materials reach the plastic level only when stress is applied, this stress level at which the deformation occurs is called the yield point from this the point as mentioned before the material cannot be bought back to its original shape. After the material has reached its maximum limit, the object will no longer stretch; but instead will break which is called the fracture point. This is the point where the material has reached its maximum deformation and cannot go any further.

Materials:

Acrylic {Appendix 4a} Polycarbonate (Lexan) {Appendix 5a} Nylon {Appendix 6a}

Apparatus:

UTS tester (20 kN load cell) Vanier Caliper (to measure the thickness and width of samples) Grinding Paper (for grinding the edges of nylon for proper gripping)

Procedures:

1. The digital Vanier Caliper was used to measure the gage size, width and thickness of each given sample.

2. Power of the united machine the controller was turned on.3. The datum program was run on the computer.4. The jaws were jogged by clicking operate -> jog as needed to load the sample.5. Sample was properly loaded in between of the jogs.

Note: For Nylon, the edges were grinded by grinding paper for proper grip.6. In the window of datum software, new test sample was created by clicking “new” and

a name was given to the file.7. Under the template tab, “metric unit” was chosen.8. Under the sample info tab; the name of the sample was typed, the measured width and

thickness was typed, and finally the area was found by clicking the “enter” button.9. The extension was zeroed by clicking “Pos” and entering 0.10. Force was zeroed by clicking “Force” and entering 0.

11. For the proper grip between the jaws sanded the piece of sample from both ends.12. Take one sample from the give three samples. Set one side of this part in the upper

jaw and with help of right hand side switches on the united machine set the jog machine up and down as needed and fits the other side of sample in the lower end of jaw.

13. Make sure both the ends of jaw are locked and the part in-between of both jaws is unable to move.

14. After clicking test, the machine was started.15. When the machined stopped, the sample was removed and “okay” was clicked on

computer screen.16. The graphs were saved.17. Under report tab, “report” button was clicked which popped up Microsoft Access.18. From Microsoft Access, recent test graph was clicked, after “reports” was clicked,

and finally save.19. The steps were repeated for remaining two samples.

Data:

Sample Width Thickness Gage sizeAcrylic 12.24 mm  2.96 mm 27.24mmPolycarbonate (Lexan)

13.38 mm 3.18 mm 27.22 mm

Nylon 13.57 mm 3.02 mm 27.21 mm

Tensile Properties of Acrylic:Yield (N) 2,252.59Yield Str. (mpa) 62.17Tensile (N) 2,270.64Tensile Str. (mpa) 62.67Modulus of Elasticity (mpa) 2,391Break Elong (mm) 2.909Yield Elong (mm) 2.885

Tensile properties of Nylon:Yield (N) 2,579.72Yield Str. (mpa) 60.86Tensile (N) 2,634.27Tensile Str. (mpa) 62.14Modulus of Elasticity (mpa) 1,757Break Elong (mm) 54.6Yield Elong (mm) 7.969

Tensile properties of polycarbonate (lexan):Yield (N) 2,586.73Yield Str. (mpa) 63.46Tensile (N) 2,586.73Tensile Str. (mpa) 63.46Modulus of Elasticity (mpa) 1,060Break Elong (mm) 34.386Yield Elong (mm) 4.903

Calculations:

Acrylic:

Young’s modulus for Acrylic:

Width: 12.24mm, Thickness: 2.96 mm, gage size (the size between the two radius): 27.24mm

Y = Yield X Initial length Area * Yield elongation

Measured value comes out to be = 2.391 X 10⁹ N/m²

Yield Stress, σ = Fn / A   where , Fn  = Yield Force = 2252.59 N 12.24 mm X 2.96 mm = 62.174 N /mm²Toughness:Toughness of a material = Area under the stress strain curve or area of triangle ABC

Area of triangle ABC= BC X AC

4 X Initial length X Area of material

= 2.909 mm X 2270 N 4 X 27.24 mm X 12.24 mm X 2.96 mm

= 6603.43 N/mm² 3947.664384 = 1.6727435 N/mm²

Final size of sample at the break point = Break Elong + Gage size = 2.909 mm + 27.24 mm = 30.149mm

Nylon :

Young’s Modulus:

Width: 13.38, 3.18 (thickness), Gage size (27.22)

Y = Yield X Initial length Area * Yield elongation

Measured value comes out to be = 1.757 X 10⁹ N/m²

Yield Stress, σ = Fn / A   where , Fn  = Yield Force = 2579 N 13.38 mm X 3.18 mm

= 60.6133 N/mm²

Toughness:

Toughness of Nylon= Area under the Force vs extension curv Initial length of nylon X Area of Nylon

Area under the force vs extension curve-

Total area is approximately = Ar.(AOZ)+Ar.(AIB)+Ar.(AINO) + Ar.(BHMN) + Ar.(BCH) + Ar.(CHD) + Ar.(HDMY) + Ar.(DJE) + Ar.(JEYK) + Ar.(EFRK)+Ar.(FPG) + Ar.(PGRQ)

= ¼ x 2000x3 + ¼ x (2557.7 – 2000)(7.6 – 3) + (7.6 – 3)(2000) + (10.4-7.6)(2557.7) + ¼ (2557.7-2500)(10.4-7.6) + ¼ (13.7-10.4)(2557.7-2500) + (13.7-10.4)(2557.7) + ¼ (19.3-13.7)(2557.7-2336.5) + (19.3-13.7)(2336.5) + (52-19.3)(2336.5) + ¼ (54.4-52)(2336.5-1346) + (54.4-52)(1346) =120653.6475 N.mm

Therefore toughness = Total area___________________Length of nylon sample X area of sample

= 120653.6475 N.mm13.38 mm X 3.18 mm X 27.22 mm

= 104.176 N/mm²

Final size of sample at the break point = Break Elong + Gage size = 54.60 mm + 27.21 mm = 81.81 mm

Polycarbonate (Lexan):

Young’s modulus for Lexan:

Width: 13.57, 3.02 (thickness), Gage size: 27.21Y = Yield X Initial length Area * Yield elongation

Measured value comes out to be = 1.060 X 10⁹ N/m²

= 55.4808 %

Yield Stress , σ = Fn / A   where , Fn  = Yield Force = 2586.73 N 13.57 mm X 3.02 mm = 63.1196 N/mm²

Toughness:Toughness of Lexan sample = Area under the Force vs extension curve Initial length of lexan X Area of lexan

Area under the force vs extension curve:

Area = Ar.(ANE + ACB + CBFE + BOM + OMGF + MLHG + JLK + LKIH)

= ¼ (5)(2586.73) + ¼ (5.75-5)(2586.73-2169.8) + (5.75-5)(2169.8) + ¼ (8.75-5.75)(1971.7) + (8.75-5.75)(1971.7) + (24-8.75)(1971.7) + ¼ (34.375-24)(2330.2-1971.7) + (34.375-24)(1971.7) = 63787.484 N.mm

Toughness of Laxen = Area under the Force vs extension curve Initial length of lexan X Area of lexan

= 63787.484 N.mm 27.21 mm X 13.57 mm X 3.02 mm

= 57.2032 N/mm²

Final size of sample at the break point = Break Elong + Gage size = 34.386 mm + 27.22 mm = 61.61 mm

Observations:

After conducting the tensile tests for all samples; it was noted that the Acrylic took the least amount of time to “snap” (reach fracture point) {Appendix 4b}, while polycarbonate (Lexan) took some time to reach its fracture point {Appendix 5b}, and the nylon did not fully snap into two pieces {Appendix 6b}.

Discussions:

Before using the UTS tester, the observers stated that nylon plastic should be the most ductile since it was bending by applying force on it by hand; while Lexan should be second most brittle (the material was bending after applying force by hand, but not as much as nylon), and acrylic is the hardest since it had a narrow bend after applying force by hand was the hardest. After using the UTS tester on the three samples; one may say that the statement made before the test is correct after looking at the break elongation of the three samples. The definition of break elongation is the difference between the final size and initial size of the sample; it tells one how much a sample is deformed. Out of the three samples, the Break Elong of Nylon is the most, polycarbonate (Lexan) has second most, and Acrylic has it the least. Thus, higher the Break Elong the more ductile is the material; since according to the book Material Science, “ductility is the amount of permanent deformation occurred when the material reaches its breaking point” (Kakani 215). There are also many other materials properties that can be found with the help of Young’s modulus, breaking load, and yield load. According to the textbook Material Science and Engineering by William D. Callister (2011) and David G. RethWisch (2011), the Young’s modulus is the ability to measure the stiffness of an object (G9). The more the stiff the material is, the more Young’s modulus it has, and the least strong it is since it requires less force (aka the break load) to break it (Shercliff). Looking at the results of the Young’s Modulus and break loads; one may say that the Nylon is the strongest material among the three samples. It has the most break load among the three and the second youngest modulus among three*. This statement also proves that the acrylic is the least strong and most stiff material among the three since it has the least force applied to break it and has a really high Young’s Modulus.*NOTE: Reason for Nylon’s high Young’s Modulus will be discussed afterwards.

As mentioned in theory, yielding is the point the deformation starts. So the yield load is the amount of force applied by the tester on the sample to reach the yield point. As per the results collected by the UTS tester, the yield load is the maximum in the polycarbonate (Lexan), second most in nylon, and least in acrylic. These results shows that polycarbonate (Lexan) is the hardest among the three samples since it requires the most force to deform permanent (which explains why are they used in making bullet proof windows); while the acrylic is the least hard and most brittle among the three samples since it required least force to deform and break afterwards.In addition, the consumption of Carbon Fibre filler in Nylon and polycarbonate (Lexan) also affects the elastic modulus (thus the ductility) of the two samples. The journal CHARACTERIZATION AND TENSILE MODULUS MODELING OF CONDUCTIVE RESINS by Jeremiah Paul Konell explains the effect of increasing the volume content of Cabon Fiber fillers increases the elasticity modulus of both Nylon and Lexan since the Carbon fiber has the “highest aspect ratio” (Konell 78) {Appendix}. With relationship to this lab, the volume intake of Carbon fibre filler was more in Nylon than in polycarbonate (Lexan) which increased the Young’s modulus of Nylon.Note: Nylon could not reach a full fracture point because of the texture of the material, the Nylon sample was slightly slipping (even after grinding the edges) from jaws.

Difficulties faced during lab: There was only one difficulty faced during the lab the slipping of nylon sample from the jaws of the tester. The texture of nylon was so smooth that it was slipping from the jaws while the test was being run on the sample. This may have altered with the results of the sample, thus giving the observers wrong conclusions about the lab. To avoid this difficulty for future, a rougher texture of Nylon sample should be used which will not even after grinding the edges it will not slip.

Percentage Error:

1. Acrylic:Measured value = 2.391 X 10⁹ N/m²

Internationally accepted value of Young’s modulus for Acrylic= 3.2 X 10⁹ N/m²(Peer review journal- http://www.matweb.com/reference/tensilestrength.aspx)

Therefore percentage error = (Actual value – Measured value) X 100 % Actual value = 3.2 X 10 ⁹ - 2.391 X 10 ⁹ 3.2 X 10⁹

= 25.28 %2. Lexan:

Measured value comes out t be = 1.060 X 10⁹ N/m²

Internationally accepted value of Young’s modulus for Lexan = 2.6 X 10⁹ N/m² (Peer review journal- http://www.matweb.com/reference/tensilestrength.aspx)

Therefore percentage error = (Actual value – Measured value) X 100 % Actual value

= (2.6 X 10 ⁹ - 1.060 X 10 ⁹ ) X 100 %

2.6 X 10⁹= 59.23 %

3. Nylon

Measured value = 1.757 X 10⁹ N/m²

Internationally accepted value of Young’s modulus for Nylon = 2.5 X 10⁹ N/m² (Peer review journal- http://www.matweb.com/reference/tensilestrength.aspx)Therefore percentage error = (Actual value – Measured value) X 100 % Actual value = (1.8 X 10 ⁹ - 1.757 X 10 ⁹ ) X 100 %

1.8 X 10⁹ = 2.39 %

Sources of Errors:

1. Measurement Error: The dimension of thickness and width of the samples were not measured properly. The wrong dimensions might have given the computer to use the wrong stress force to apply to the sample which did not give us the Young’s modulus from the reference.

2. The Fracture point of samples: The fracture point of the samples occurred at the upper radius of the samples instead at (or near) the centre of the gage size; this is probably because of the way these samples were manufactured. This would have altered with the Young’s modulus since it would have been easier to break it from the edges instead of the centre.

Conclusion:

An UTS tester was used to check and compare the tensile of three samples (Acrylic, Nylon, and Lexan). After doing the experiment and comparing the tensile properties, it was noted that the Lexan was the most ductile, Nylon being the second most brittle, and acrylic being the hardest.

There observers encountered errors like measurement and manufacturing which might have altered the results and given them wrong values for some of the samples. The UTS tester is an easy and safe machine that can be used to examine the material properties like brittleness and hardness of various materials in the world. With the help of the machines, many industrial markets will know which material will be suitable for making their product. For example, nylon is used to make fabrics in textile industries, fishing nets, ropes, and parachutes. It is also used in making swim vest bullet vests, tires, and combats uniform since it is a high strength fibre. While polycarbonate (Lexan) are lightweight alternatives to glass is used to make things such as helmets, bullet proof glass, data storage systems (dvds), food containers, and electronic component (electrical/telecommunications hardware and also as dielectrics in capacitors). Finally, Acrylic is used automotive parts, appliances, lighting fixtures, household goods (40), and medical/healthcare applications (lenses).

APPENDIX Appendix 1: UTS testser

Appendix 2: Different regions on a stress-strain curve

Appendix 3:1. Strain: The change in gauge length of a specimen (in the direction of an applied

stress) divided by its original length. (G13, Material Science and Engineering)2. Stress: The instantaneous load applied to a specimen divided by its cross-sectional

area before any deformation. (G13, Material Science and Engineering)

Appendix 4: a- acrylic sample, b- sample after test

Appendix 4: a- polycarbonate (Lexan), b- sample after test

Appendix 6: a- nylon sample, b- sample after test

a b

ab

Work Citied

Callister, William D., and David G. Rethwisch. Materials Science and Engineering. New York, NY: Wiley, 2011. Print.

Saleh, Safaa, Dr. "4.4 Experiment 4: Tensile Test of Plastic Sample." Materials Engineering Laboratory Book. Brampton: Sheridan College, 2014. 11-14. Print.

Kakani, S. L. Material Science. New Delhi: New Age International (P) Limited, 2004. Print. Konell, Jeremiah Paul. Characterization and Tensile Modulus Modeling of Conductive

Resins. N.p.: n.p., 2002. Print. Croucher, Phil. JAR Professional Pilot Studies. S.l.: S.n., 2007. Print. "Property Information." Property Information. N.p., n.d. Web. 04 Feb. 2014.

<http://www-materials.eng.cam.ac.uk/mpsite/properties/non-IE/stiffness.html>. http://www.toolingu.com/definition-500120-83827-plastic-region.html http://www.matweb.com/reference/tensilestrength.aspx http://www.preservearticles.com/201101032306/uses-of-nylon.html http://www.ask.com/question/what-is-polycarbonate-used-for http://plastics.ides.com/generics/3/acrylic-acrylic http://www.lairdplastics.ca/product/materials/polycarbonate http://www.ask.com/question/what-is-the-use-of-nylon