Tear Strength
What is fabric tearing? Have you ever noticed that if a piece of fabric gets a small cut by any sharp object, it has a hole? This punctured fabric can easily convert into a long rip using extra pull. This is a common type of strength failure in a fabric.
Definition
“Tear strength is the amount of force that is required to rip the fabric. It depends upon the strength of fabric.”
Formula
Tear Strength calculation = Tearing Force (N) × Tearing Distance (m)
Evaluation of tear resistance is very important in industrial fabrics that are used for rough handling, such as tents, sacks, and parachutes, where high tear resistance is required.
On the other hand, some applications require low-tearable fabric, such as adhesive tapes and bandages.
Factors Affecting Tear Strength
There are the main factors that affect the tear strength of the fabric.
Yarn Strength
Single thread strength is very important for tear strength because the overall strength of fabric wear and tear depends upon the strength of the thread or yarn twist. Fabric made with good yarn strength has higher tear strength.
Fabric Weave & Structure
Smooth yarn and loose fabric structure give higher tearing strength to the woven fabric. Fabric weave plays a vital role in case of tear strength. Plain weave has lower tear strength as compared to twill and matt weave fabric structures.
Heat Setting
High Heat setting reduces the thread strength, which causes to drop in tear strength.
Special Finishes
Special fabric finishes like drip-dry and crease-resistant treatments may reduce the tear strength.
Tear Strength Testing Methods
There are three major methods to determine the fabric’s tear strength in a fabric testing laboratory.
- Trapezoidal Method (ASTM D624)
- Elmendorf Method (ASTM D1424)
- Tongue Method
- Single Tongue Method
- Double Tongue Method
Trapezoidal Method (ASTM D624)
In a trapezoidal tear testing method, a trapezoid is drawn on the fabric sample in a cloth testing laboratory. The clappers of the tear strength tester clamp the two hypotenuses of a trapezoid.
After setting the sample, an increasing force is applied to the sample to tear along the width direction. In this way, the average maximum tear strength is tested.
For taking best results, 5 samples should be taken from the different positions of the fabric in each side from longitude and latitude. These samples are cut with the size of (150mm +2 mm) × (75 mm + 2 mm).
The distance between two clamps is set to (25 mm + 1 mm), and the stretch speed is set to 100 mm/min.
The appropriate loading range is chosen to fulfill that tear strength will fall on 10 – 90% of the total span. The sample is clamped along the hypotenuse of a trapezoid to make the notch line in the middle of two clamps.
There are two sizes of clamps. One side clamp’s size is 100 mm, while the other side of the trapezoid clamp’s size is 25 mm. A small cut of 15 mm is done on fabric on a smaller side clamp.
The fabric sample on the short side is kept tight, and the long side is kept with wrinkles. Now, turn on the fabric lab test machine. As the lower clamp goes down, each yarn of the sample faces stretches one after another.
The force spreads from the notch line to the long side clamp till the fabric sample tears completely. This is the whole procedure of the trapezoidal tear testing method for making fabric lab test reports.
Elmendorf Method (ASTM D1424)
In the Elmendorf testing method, a sample of (102 mm × 75 mm) is cut from the testing fabric in the textile lab. The testing fabric should be a minimum of 01 meter in length, conditioned for 04 hours at 21 + 1 C and 65 + 2 relative humidity.
The specimen is cut from 150 mm beyond the edges of the fabric for both warp and weft directions. Two sets of samples, each with 5 specimens, are ready for longitude and latitude testing.
Elmendorf tester has jaw clamps, a blade for small cuts of 20mm on the specimen, and a weight range of 8N, 16N, 32N, 64N, and 128N for lower to higher tear strength fabrics.
Turn on the machine. Calibrate it, and set the parameters. Put the weight in the tester weight holder according to the strength of the fabric. Place the specimen into the jaws and tighten it firmly. Now press the button to operate the fabric tests.
Specimen tears by the weight of the pendulum. Monitor the specimen tearing behavior, record the values and mention in the report.
Tongue Method
The tongue method is divided into two different methods: Single tongue method and double tongue method. The most commonly used tongue method is the single tongue method. The sample is mounted in a tear tester. The notch line is kept straight between the up and down clamps.
The tester is turned on. The tension is applied toward the notch line. The tear strength is recorded that tears the fabric sample.
Single Tongue Method
Two sets of samples are taken from the Warp and Weft sides of the fabric. Each set has a minimum of 5 samples that are cut from different positions of the fabric. It is done to avoid taking the same yarn in length and width direction.
For the single tongue method, rectangular fabric samples are cut with the size of (200 mm + 2 × 50 mm + 1 mm). Each rectangular sample is cut 100 mm parallel to the length direction from the center of the width side.
The tear terminal should be marked at 25 mm + 1 mm from the center distance of the sample to the uncut end. The length of the span is set to 100 mm, and the stretched speed is 100 m/min. The sample is mounted in clamps.
One side of the specimen from the cut is held in one clamp, and the other side of the sample from the cut is held in another clamp. The cutting line should align with the center line of the clamps. The uncut end is kept in a free condition.
It should be ensured that two legs by the cutting end are fixed in clamps. The tear should be parallel to the notch for accurate results when it starts tearing. Now, tear force is applied to tear the fabric completely. The results are taken.
Double Tongue Method
In the double tongue method, the specimen is cut from the center and again takes a small rectangular shape from the specimen. The small rectangular fabric sample is held in one jaw, and the other side of the specimen is held in the second jaw.
When clamping, the sample tongue is clamped in the center of the clamps, symmetrical to make the line bc visible. Two legs of the sample, parallel to the direction of tearing, are clamped symmetrically in removable clamps to make lines ab and cd visible.
It should be ensured that each tongue is fixed in clamps so that tearing should be parallel to the tear direction when the fabric is stretched. Start the machine. Tearing is pulled to the end marks of the sample.
The tearing strength and tearing length of each sample are noted. The main point is you should focus on the tearing direction. Either the sample tears in the direction of applied force or the yarns slip away from the fabric.
If the sample does not slip away from the clamps and tear takes place in the direction of applied force, then results are conducted. Otherwise, the test should be revised.
Significance of Tear Strength
Tear strength is an important mechanical property and quality parameter of fabric in the textile industry as well as the medical, automotive, and aerospace industries. The tear strength test ensures the durability, quality, and safety of the fabric.
Here is the significance of tear strength according to the use of fabric in different industrial sectors.
Apparel
Tear strength ensures the garment’s better lifespan and comfort.
Industrial Textiles
Fabric tear strength test is a very important parameter for industrial textiles that are used in construction and safety equipment.
Medical Textiles
In medical textiles, somewhere, we need low-tear fabric like bandages and tapes. While some other cases, we need high tear fabric, for medical devices, implants, and protective clothing.
Automotive
High-tear textile is required for implanting upholstery, seat belts, and airbags.
Aerospace
It is a very important parameter in aerospace for lightweight and high-strength materials.
Tensile Strength
What does tensile strength mean? The tensile strength of a fabric gives us an idea of how much force a fabric can withstand. If the fabric strength is poor, then it will break with excessive tensile force. The strength of a fabric varies with EPI, PPI, and count variation.
Definition
“Tensile strength of a fabric is the maximum force that a fabric can withstand before breaking, under tensile stretch.”
Formula
Tensile Strength = Tensile Force (N)
Cross-sectional Area (A)
Fabric weave also has a major affect on the tensile fabric clothing strength. For example, plain fabric has higher tensile strength as compared to twill fabric if its end/pick and yarn count are the same.
Tensile Strength Testing Methods
There are two methods used to evaluate and explain the tensile strength of the fabric.
- Strip Test Method (ASTM D5034)
- Grab Test Method (ASTM D5035)
Strip Test Method (ASTM D5034)
In this method, the fabric stripe is extended to its breaking point by a tensile tester, which can record the breaking load and extension. Similarly to previous tests, 05 samples are taken from the testing fabric at different places for each direction warp and weft.
The specimen is cut with the size of (60 mm × 300 mm) and then shredded from the edges to get a 50 mm wide specimen. The rate of extension is set to 50mm/min, and the gauge length is 200 mm. Prevention is 1% of the probable breaking load.
There are two jaws, one is fixed while the other has load cell which stretches the specimen. In the 50 mm of specimen is placed inside the jaws from one end, similarly on the other end 50 mm is placed inside the fixed jaw.
So the remaining sample is 200 mm, that’s why we call gauge length is 200 mm. Now, turn on the tester. The jaw with load cell will stretch the specimen until it breaks. Record the values and tearing behavior.
Precautions
- If the specimen breaks within 5 mm of the jaws or at loads substantially less than the average, then this test will be discarded.
- The mean breaking force and mean extension % of initial length are reported.
- Samples are cut (60 mm × 300 mm) parallel to warp/weft.
- Threads are shredded from both sides of the specimen’s width to bring down to 50 mm wide.
- Heavily milled fabrics do not require fraying. Its sample is cut with size of (50 mm × 300 mm).
Grab Test Method (ASTM D5035)
The grab test uses jaw faces, which are considerably narrower than the fabric, so avoid the need to fray the fabric to width, hence making it a simpler and quicker test to carry out.
The specimen is cut with the size of (100 mm × 150 mm). The jaw size is 25 mm square, which stresses only the central 25mm of the specimen.
A line is drawn 37.5 mm from the edge of the fabric to assist it in clamping so the same set of threads are clamped in both jaws.
The gauge length is 75 mm, and the speed is adjusted so that the sample is broken in 20 + 3 seconds
In this test, there is a certain amount of assistance from yarns adjacent to the central stressed area so that the strength measured is higher than for a 25 mm frayed strip test.
Grab test is fundamentally different from strip test.
In the grab test, aw faces are considerably narrower than the fabric. Here is no need to fray the fabric.
Grab test is a simpler and quicker method.
Significance of Tensile Strength
Tensile strength is another mechanical property and an important parameter of fabric in the textile industry, as well as in other industries like the medical, automotive, and aerospace industries.
Structural Integrity
Fabric tensile strength test ensures the structural integrity of the fabric and any other material that is used in infrastructures that can withstand the load.
Apparel
Fabric with good tensile strength has more durability, comfort, and performance.
Industrial Textiles
Tensile strength is crucial for industrial textiles that are used in construction, building, and bridges.
Medical Textiles
Good tensile strength material is used in surgical instruments and medical devices.
Automotive
High-tensile textile is required for implanting upholstery, seat belts, and airbags.
Aerospace
High tensile strength is required in aerospace for lightweight and high-strength materials.
Key Differences between Tear Strength and Tensile Strength
Tear strength and tensile strength are mechanical properties of fabric that ensure the stability of the fabric against load and tension. Here, we will discuss the main differences between these two parameters.
Tear Strength
- Tear strength is more focused in that application where the textile faces dynamic force or undergoes from sharp objects. In these cases, tear strength is the resistance of a fabric to puncture or tear.
- It evaluates the fabric’s strength to withstand localized stress.
- It determines the material’s ability to resist crack propagation
- Trapezoidal, Elmendorf, and Tongue tear Methods measure tear strength.
- Units of tear strength are Newton (N), Pound (lb), or Gram-Force (gf).
- Tear strength is a more important parameter for application in textiles, flexible plastics, and composites.
Tensile Strength
- Tensile strength is subjected to focus in those applications where the textile faces constant tension or stretching forces. In these cases, tensile strength is the resistance of a fabric to pulling or stretching forces.
- It evaluates the fabric’s strength to withstand uniform stress.
- It determines the material’s ability to resist deformation.
- The strip-and-grab test method measures tensile strength.
- Units for tensile strength are Mega Pascal (MPa), Pounds per Square Inch (PSI), or Newton per Square Millimeter (N/mm²).
- Tensile strength is a more important parameter for application in structural materials, fibers, and films.
Important Relation between Tear and Tensile Strength
It is experienced that a fabric or material with high tensile strength mostly also has high tear strength. However, it is observed that a high tear-strength fabric does not always have high tensile strength.
Applications and Practical Implications
Here is a practical example of tear and tensile strength implications.
Tear Strength
Tear strength’s main application is athletic wear and outdoor textiles like tents or tarpaulins. For example, in athletic wear, tear strength ensures that fabric will withstand forces when an athlete stretches his body.
Higher tear strength helps tents withstand wind stress, heavy rain, and potential damage from sharp objects and branches.
Tensile Strength
Tensile strength’s main application is automotive textiles. For example, the fabric used in automotive upholstery and seat belts must withstand regular force and pressure, which is only possible with high-tensile strength fabric.
Higher tensile strength fabric is used in conveyor belts and safety equipment for worker safety and material durability.
Conclusion
Tear strength is the amount of force that is required to rip the fabric. It depends upon the strength of the fabric. However, the Tensile strength of a fabric is the maximum force that a fabric can withstand before breaking under tensile stretch.
Tear strength is tested by Trapezoidal, Elmendorf and Tongue tear Methods, while Strip and Grab test methods test Tensile strength.
FAQs
What is Tear Strength?
Tear strength is the amount of force that is required to rip the fabric. It depends upon the strength of the fabric.
What is the fabric tear strength formula?
Tear strength is calculated by using this formula.
Tear Strength = Tearing Force (N) × Tearing Distance (m)
What are tear strength units?
Tear strength units are Newton (N), Pound (lb), or Gram-Force (gf).
Why tensile strength is important for the fabric?
Tearing strength is important for the fabric in those applications where the textile faces dynamic force or undergoes from sharp object. In these cases, tear strength is the resistance of a fabric to puncture or tear.
What are the ASTM methods for tear testing of fabric?
- Trapezoidal Method (ASTM D624)
- Elmendorf Method (ASTM D1424)
- Tongue Method
What is the main application of tear strength?
Tear strength’s main application is athletic wear and outdoor textiles like tents or tarpaulins.
What is Tensile Strength?
The tensile strength of a fabric is the maximum force that a fabric can withstand before breaking under tensile stretch.
What is the fabric tensile strength formula?
Tensile strength is calculated by using this formula.
Tensile Strength = Tensile Force (N)
Cross-sectional Area (A)
What are tensile strength units?
Tensile strength units are Mega Pascal (MPa), Pounds per Square Inch (PSI), or Newton per Square Millimeter (N/mm²).
Why tensile strength is important for the fabric?
Tensile strength is important physical testing of fabric in those applications where the textile faces constant tension or stretching forces. In these cases, tensile strength is the resistance of a fabric to pulling or stretching forces.
What are the ASTM methods for Tensile testing of fabric?
- Strip Test Method (ASTM D5034)
- Grab Test Method (ASTM D5035)
What is the main application of Tensile strength?
Tensile strength’s main application is automotive textiles. For example, the fabric used in automotive upholstery and seat belts must withstand regular force and pressure, which is only possible with high-tensile strength fabric.
Does Wet or Dry Fabric Testing Make a Difference in Tensile Strength?
Yes, it depends upon the nature of the fabric. It is observed by experiments that in some types of fabrics, wet fabric has more tensile strength as compared to dry fabric. For example wet cotton is stronger than dry cotton in tensile strength.
Tensile and Tear Strength May Change Over Time.
Yes, both characteristics of a fabric may change over time due to various factors. These factors include aging, fatigue, UV radiation, chemical exposure, moisture, and temperature.
It is observed by experiments that tear and tensile strength decreases with the passage of time. However, some materials may exhibit an increase in tensile strength due to fiber orientation or crystallization.
Related Resources
Insights and experience on ASTM D2261 Tearing Strength of Fabric
A Practical Guidance on ASTM D5035 Breaking Strength and Elongation of Textile Fabrics