Different industrial techniques employed to determine the tensile strength of variety of polymers and factors that affect these values.

1. Tensile Strength
- Estimation methods, Principles and
Factors affecting the values.
-Omkar Kshirsagar
-Saket Mulge
-Renuka Patil
-Sravya Nuguri

2. Introduction
 One of the fundamental methods in
material science.
 Sample is subjected to controlled
tension until failure.

3.  Results are used for the selection of materials for various
purposes considering how it will react under different types of
forces.
 Properties measured – UTS (Ultimate Tensile Strength),
Maximum elongation, Reduction in area.
 From these properties following properties can be determined:
Young’s Modulus, Poisson’s Ratio, Yield strength
 Uniaxial tensile testing – Isotropic materials
 Biaxial tensile testing – Composite materials
Introduction

4. What is Tensile Testing
 Tensile testing is a way of determining how something will
react when it is pulled apart - when a force is applied to it
in tension.
 Tensile testing is one of the simplest and most widely used
mechanical tests. By measuring the force required to
elongate a specimen to breaking point, material properties
can be determined that will allow designers and quality
managers to predict how materials and products will behave
in their intended applications.
 Along the tensile profile there are many points of interest,
chief among them the elastic limit and force to break or
failure point.

5. Standard Polymer Tensile Testing Methods
 D638 - Test Method for Tensile Properties of Plastics.
 D5083 - Fiber-reinforced thermosetting laminates.
 D882 - Thin Plastic Sheeting.
 D1922 - Tearing resistance of various plastic films and thin
sheeting by Pendulum method.
 D412 - Vulcanized Rubber and Thermoplastic Elastomers.
 D3039/D3039M - Polymer Matrix Composite Materials.

6. Types Of Tensile Testing
 Adhesion/Bond Strength
 Crimp joint pull-off force
 Peel
 Tear resistance

7. Advantages Of Tensile Testing
 Tensile testing provides data on the integrity and safety of
materials, components and products, helping manufacturers
ensure that their finished products are fit-for-purpose and
manufactured to the highest quality.
The data produced in a tensile test can be used in
many ways including:
 To determine batch quality
 To determine consistency in manufacture
 To aid in the design process
 To reduce material costs and achieve lean manufacturing goals
 To ensure compliance with international and industry standards

8. Basic Approach
 Step 1: Original shape and size
of the specimen with no load.
 Step 2: Specimen undergoing
uniform elongation.
 Step 3: Point of maximum
load and ultimate tensile
strength.
 Step 4: The onset of necking
(plastic instability).
 Step 5: Specimen fractures.
 Step 6: Final length.

10.  Cut or injection mold your material into “dog bone” shape under 14mm
thickness.
 Load the specimen into tensile grips.
 Begin the test by separating the tensile grips at a constant rate of speed.
 Speed can range from 0.05 – 20 inches per minute.
 The target time from start of test to break should be from 30 seconds to 5
minutes.
 End the test after sample break (rupture)

11.  Thin Plastic Film less then 1mm in thickness
 Load your sample into your grips.
 Enter your specimen geometry (width,
thickness, and gage length) into your
controller.
 Speed : 20inch/min

12.  Sample is a 63mm x 76mm rectangle
 The energy loss by the pendulum is used
to calculate an average tearing force.
 Test results are presented as tearing
force in milli-newtons.
 Tearing force lies in the range of
0-800 gram force.
 Sample thickness is also reported.
 Only results for samples of the
 same thickness can be compared.

13.  Specimens are placed in the grips of a Universal Test
Machine at a specified grip separation and pulled until
failure.
 For ASTM D5083 the test speed may be determined
by the material specification.
 The default test speed is 5 mm/min.
 Depending upon the reinforcement and type, testing in
more than one orientation may be necessary.
 The standard specimen has a constant rectangular
cross section, 25 mm wide and at least 250 mm long.
 Thickness can be between 2 mm (0.079 in) and 14
mm.

14. Factors Influencing Tensile Strength
 The effect of additives and impurities
 Temperature
 Geometric size and shape
 Orientation and Morphology
 Surface Condition
 Energy and speed of loading
 The environment- Humidity.
 Strains in the article due to external loads
 Gauge Length
 Jaw Slippage, deformation due to jaw pressure
higher strain at the neck of the specimen
contribute to the error.

15. Stress-strain graphs of two plastics
(a) A rigid polymer at a temperature below Tg- High tensile strength but less area under sress
strain graph
(b) An amorphous polymer greater than Tg –low tensile strength but more area under stress
strain curves

16. Tensile strength increases with
Effect Of Temperature:

17. Effect of Additives

18. References:
• The Effect of Temperature and other Factors on Plastics and Elastomers
-By Laurence W. McKeen
• Effect of temperature on tensile properties of injection moulded short
glass fibre and glass bead filled ABS hybrids
- S.Hashemi
• Fundamentals of Material Science and Engineering
• ASTM website
• www.testresources.net
• www.ptli.com