Penetration testing is very similar to compression testing with one key difference, the penetrometer probe is typically much smaller than the sample being tested and passes completely through a sample (e.g. a hypodermic needle through an elastomeric closure).
It may also be considered a penetration test if it passes through an element of the product (e.g. an outer layer of a composite material).
Puncture testing is similar, meaning the probe passes into the sample, though not necessarily exiting.
This test method can be performed on a wide variety of products and is very useful in comparative analysis of the energy required to rupture or deform a material..