What is an impact test for plastic?
Impact tests according to the Charpy method are used for the characterization of a plastic material at high strain rates. The load application is abrupt and carried out in a 3-point flexure fixture. In the classic method, the result is presented in terms of the energy absorption of the specimen.
What impact test is used for polymers?
The conventional tensile-impact test is standardized in the ISO 8256 standard. It is the uniaxial tensile test with a relative high strain rate which is generally used for that polymers that are too flexible or too thin for Charpy or Izod impact test.
How do you calculate Charpy impact strength?
Test formula
- The Knotch Impact Energy KV = mgH – mgh.
- m – Mass of the Pendulum.
- H – Height of Pendulum starting point.
- g – Gravity.
- h – Height of the pendulum from the first reversal point.
What is impact test machine?
Impact testing machines evaluate an object’s capacity to withstand high-rate loading and it is commonly used to determine the service life of a part or material. Impact resistance can be among the most challenging qualities to measure. There are two standard kinds of impact test: Charpy and IZOD.
What are the major reason for testing in plastic?
Testing plays a critical role in the life cycle of a polymer, from the raw material to the compound through to the semi-finished and finished product.
What is the toughest plastic material?
Polycarbonate is the strongest plastic that is 200 times stronger than glass and is warranted against breakage or cracks. With its high impact strength, it is ideal for structures that are in places where there is snow or hail so that the building is not impacted by such throws.
What is the unit of impact energy?
ASTM impact energy is expressed in J/m or ft-lb/in. Impact strength is calculated by dividing impact energy in J (or ft-lb) by the thickness of the specimen. The test result is typically the average of 5 specimens. ISO impact strength is expressed in kJ/m2.
What is the depth of notch in impact test?
The standard Charpy-V notch specimen is 55mm long, 10mm square and has a 2mm deep notch with a tip radius of 0.25mm machined on one face.
What is Charpy test used for?
The Charpy impact test, also known as the Charpy V-notch test, is a standardized high strain-rate test that determines the amount of energy absorbed by a material during fracture.
What precautions should be taken in Charpy impact test?
As such, there are no special precautions to be taken except the placement of sample in the fixture. If the V-notch is too high or too in the clamp, the test results will not be accurate. If the sample is too high, the strength calculated is too low than actual.
Why do we use V notch in Charpy impact test?
Charpy also found that the use of a notch in the test specimen was crucial in increasing the sensitivity and reproducibility of the measurement. His name became associated with the Charpy Impact Test for notch toughness because he spent years thoroughly investigating the parameters of the test.