Puncture testing, performed to determine the penetration or the puncture strength of materials used in packaging, food, textiles, and medical industries, measures properties such as maximum force, breaking strength, and the penetration distance. In order to calculate the specimen puncture resistance, the specimen is first stretched and placed on the ring clamp mechanism of the puncture fixture. Load is then applied by the puncture probe until specimen rupture.
Material response to penetration varies with numerous factors including material thickness, elastic modulus, rate of penetration, temperature, shape and type of probe. Consequently, puncture testing methods are governed by standardized test procedures that specify the test set up including the rate, the specimen size, as well as the puncture probe geometry. This blog post will cover puncture testing, recommended equipment, and the test methods that outline test setups to test certain materials at the optimal test conditions.
Why is puncture testing recommended?
Depending on the industry, puncture testing can be crucial to the quality of the end product. Packaged goods are used by consumers as well as businesses in other industries such as the medical field. Products used in packaging often need to be tested in puncture to ensure the package will not burst prior to use. If the integrity of a barrier wrap is destroyed, gases, odors, and unwanted contaminates will cause potential harm to the product and reduce shelf life. By running puncture testing, quality control professionals are able to determine the deformation in the material and the stress concentrations in its different areas to ensure the end product will have adequate strength.
In the medical field, furthermore, researchers run puncture testing to test the resistance of biomaterials such as tissue engineered or synthetic skin to ensure properties match the native tissue and that, when implanted, problems won’t arise.
Note that puncture testing does not always have to be carried out in the compressive direction. Specimens can also be tested in the tensile direction by specific puncture testing fixtures where the puncture probe is mounted on the bottom instead of the top.
A universal testing machine equipped with a puncture fixture with the top probe mounted on the moving crosshead is recommended for puncture testing. The recommended constant-rate-of-extension (CRE) type universal testing machine will have puncture speeds of 0.001” per minute up to 40” per minute.
Most puncture testing is run at low rates, a universal testing machine with closed-loop control and constant-rate-of-extension will ensure the required rates are kept constant throughout the testing.
The eXpert 5000 series feature modular single and dual column frame components for a wide range of applications. Static 5000 systems include the eXpert 5601, eXpert 5602, and eXpert 5603. The eXpert 5601 systems are used for applications up to 1 kN (100 lbf) capacity, the eXpert 5602 up to 2.2 kN (225 lbf), and the eXpert 5603 up to 5 kN (500 lbf).
Puncture Test Setup on an eXpert 7600 Single Column Testing Machine
eXpert 7600 series are single column testing machines that can go up to 5kN. Similar to the eXpert 5600, three models include the eXpert 7601 for 1 kN (100 lbf) force capacity applications, the eXpert 7602 for 2.5 kN (250 lbf) force capacity, and the eXpert 7603 for 5 kN (500 lbf) capacity.
Puncture Test Setup on an eXpert 2600 Dual Column Testing Machine
eXpert 2600 series are available in table top or floor standing configurations from 2kN to 300kN. Other than the puncture test set up, the versatile design of eXpert 2600 machines allows testing in tension, compression, flexure, shear, peel, adhesion, and more with a variety of grips and fixtures.
All ADMET machines are closed-loop servo control systems, ensuring the speed is kept constant during testing. In addition, they are equipped with the eP2 controller and GaugeSafe software or the MTESTQuattro controller and software, which provide the automation and accuracy required for the standardized tests listed in this post.
Read our Puncture Testing with a Universal Testing Machine blog here.
Puncture Fixture Components
Puncture fixtures include the probe and the specimen holder. On a typical puncture test setup, the upper part includes the puncture probe secured to the load cell that is attached to the system’s crosshead, which moves down to create the puncture force. The probe comes in different diameters and heights and may also be called a plunger, needle, or ball, depending on the required dimensions. The bottom part of the fixture, or the specimen clamping mechanism, is designed to hold the specimen being punctured. Most test standards specify the required dimensions of both the plunger and the clamping mechanism to test each type of specimen. Picture to the right shows one version of a puncture fixture. The diameter of the plunger is based on the actual scenario a certain material is used for. The test standard examples below include further information on different puncture fixture specifications.
Universal testing machines can be purchased with puncture fixtures, or, if a puncture test requirement arises after the machine purchase, the fixture can be added to the setup later on. It is important to take into account the available spacing in the testing area of the testing machine prior to purchasing a puncture fixture. For single-column machines, the throat depth will determine whether the clamping mechanism of a puncture fixture will fit.
Puncture fixture modified for single column machines
Throat depth, shown on the right, is the distance between the grip adapter and the column.
If, your machine does not have adequate spacing, we offer the single column version of the puncture fix