Application Note | Puncture Resistance
Nano Puncture Resistance Using Nanoindentation
Measuring When a Thin Foil Gives Way at Millinewton Loads
Research & Experimental Testing
Jorge Ramirez
Visual Design & Editorial
Andrew Shore
Introduction
Traditional puncture tests are typically used to determine the penetration characteristics of a wide range of protective materials such as films, foils or membranes. They are widely used in the food and medical industries, in applications ranging from food packaging to rubber gloves and needles. The test is performed like a compressive test: a probe, with a choice of tips, applies increasing load until the material is penetrated, and the load at failure is recorded. These traditional tests were typically performed at higher loads, a Newton and above, with poor load control and resolution.
Importance of the Nanoindentation Puncture Test
Beyond the many traditional mechanical tests (puncture, hardness, compression, yield strength, etc.), today’s quality control environments for advanced, sensitive materials require greater precision and reliability. Traditional mechanical instrumentation fails to provide the sensitive load control and resolution required, and multiple instruments are needed for tests that can now be performed on a single system. Puncture tests, among many others, can now be run with precise resolution at nano through macro controlled loads with a single instrument.
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Measurement Objective
In this application, the NANOVEA Mechanical Tester, in nanoindentation mode, is used to study the puncture resistance of an aluminum foil sample using a cylindrical flat tip indenter. A custom sample holder was designed to secure thin film and foil samples.
NANOVEA PB1000 Large Platform
Mechanical Tester
Test Conditions
| Parameter | Value |
|---|---|
| Applied force (mN) | 400 |
| Loading rate (mN/min) | 600 |
| Unloading rate (mN/min) | 600 |
| Indenter type | Cylindrical flat |
Table 1: Test conditions.
Results
The load rose steadily as the flat tip pressed into the foil until the foil punctured at 150 mN, seen as a sudden drop in the load curve and as a circular cut in the foil (Fig. 2).
Conclusion
In conclusion, we have shown how the NANOVEA Mechanical Tester, in nanoindentation mode, provides precise measurement of puncture resistance, with a clear advantage over traditional instruments.
Other tests are possible with the same system: depth versus load also allows hardness, elastic modulus and creep to be measured with a sharp Berkovich diamond, or in a more compressive test with a sphere or flat indenter. Fatigue can be tested with multiple-cycle loading, and yield strength with multiple cycles of increasing load. With the controlled XY stage, the same instrument can measure scratch and marring properties or the coefficient of friction of these film samples, and multi-pass wear provides important information on long-term viability. Coatings on films and foils can also be studied using the lower load range of the nano module.
Frequently Asked Questions About Nano Puncture Testing
What is a puncture test?
A compressive test in which a probe is pushed into a film, foil or membrane with increasing load until it penetrates, recording the load at failure; it is widely used for food packaging, rubber gloves and needles.
Why perform it with nanoindentation?
Traditional puncture tests run at Newton loads and above with poor load control and resolution; nanoindentation gives precise control from nano through macro loads on one instrument.
How was the foil tested?
Aluminum foil was secured in a custom holder for thin films and foils and loaded with a cylindrical flat tip at 600 mN/min, to a programmed maximum of 400 mN.
At what load did the foil fail?
The foil punctured at 150 mN, seen as a sudden drop in the load curve and a circular cut in the foil.
What else can be measured on films?
Hardness, elastic modulus and creep with a Berkovich tip, compression with a sphere or flat, fatigue and yield strength by cyclic loading, and scratch, friction and wear with the XY stage.
Can coatings on films be studied?
Yes, using the lower load range of the nano module.
