The Penetration Test

The quality of a corrugated board box is not dependent on the stiffness of the material in just the machine or cross directions. During the penetration test, the material is loaded in all directions due to the pyramid formed penetrator. Therefore, the tensile, compression, bending, and shear forces, appear simultaneously. The result of this test is the energy absorbed during penetration of the material. According to recent standards, this test is performed with a pendulum impact tester or with a materials testing machine. This instrument can be used Stand Alone or connected to a computer. 

Since the penetration test with a pendulum has several weaknesses, (oscillation of the pendulum, no linear movement, no constant test speed, test results depend on the test speed, difficult handling), Zwick offers an alternative, standardized test with a material testing machine. With the linear motion penetration test (LPET), the penetration pyramid is pressed through the specimen in an even movement. The pyramid is driven and controlled by a testing machine. The force-path curve is acquired by the electronics. The result is the energy required for penetration, which is similar to the pendulum impact test.  

The standard deviation of the data due to testing machines is significantly better than that from a PET pendulum. The result correlation to PET impact testers has been evaluated in cooperation with the german wfp institute for corrugated board research and is of 5% (Standard deviation). 

Since the measurements, force and travel are acquired electronically, the measurement range is much larger than a pendulum impact test.  

Theoretically, materials from a basic weight of 80 g/m², up to heavy duty corrugated board with a thickness of 17 mm, and an energy of approx. 40 Joule, can be tested without changing weights. These characteristics make the testing machine much quicker and secure.  

Zwick Roell is working with technical paper institutes and well known industrial companies, on the industrial introduction and standardization of this test.  

The advantages: 

• Small deviation in the results 
• No changing of weights 
• No system friction 
• No erroneous oscillations 
• No manipulating hold-back collars 
• Tests can be performed on materials from 80 g/m² up to heavy corrugated board without retro-fitting 
• Ability to perform wet tests